[
  {
    "stamp": "K24",
    "metal": "gold",
    "purity": 0.999,
    "fineness": 999,
    "karat": 24,
    "region": ["JP"],
    "aliases": ["24K", "999", "999.9", "PURE GOLD", "純金"],
    "color_variants": ["YG"],
    "density_g_cm3": 19.32,
    "melting_point_c": 1064,
    "alloy_components": [],
    "valid_from": null,
    "valid_to": null,
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q897",
    "notes": "Pure gold (99.9% minimum, often 99.99% in modern bullion). In Japan stamped as K24 or 999. Too soft for most jewelry; used for investment bars, religious items, and East Asian bridal pieces.",
    "see_also": ["K22", "K18", "999"],
    "sources": ["Japan Mint hallmark standards", "ISO 9202:2019"]
  },
  {
    "stamp": "K22",
    "metal": "gold",
    "purity": 0.916,
    "fineness": 916,
    "karat": 22,
    "region": ["JP", "IN", "ME"],
    "aliases": ["22K", "916", "22ct", "22金"],
    "color_variants": ["YG"],
    "density_g_cm3": 17.7,
    "melting_point_c": 977,
    "alloy_components": ["copper", "silver"],
    "valid_from": null,
    "valid_to": null,
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1972095",
    "notes": "22-karat gold (91.67% by mass). Common in Indian, Middle Eastern, and some Japanese fine jewelry. Soft compared with K18; preferred where gold-as-investment is the buying motivation.",
    "see_also": ["K24", "K18", "916"],
    "sources": ["Bureau of Indian Standards IS 1417"]
  },
  {
    "stamp": "K20",
    "metal": "gold",
    "purity": 0.833,
    "fineness": 833,
    "karat": 20,
    "region": ["JP"],
    "aliases": ["20K", "833", "20金"],
    "color_variants": ["YG"],
    "density_g_cm3": 16.5,
    "melting_point_c": 1010,
    "alloy_components": ["copper", "silver"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "20-karat gold (83.3%). Less common than K18; occasionally seen in Japanese vintage and antique pieces, and in some Russian Soviet-era jewelry alongside the 583 mark.",
    "see_also": ["K22", "K18", "833"],
    "sources": []
  },
  {
    "stamp": "K18",
    "metal": "gold",
    "purity": 0.750,
    "fineness": 750,
    "karat": 18,
    "region": ["JP"],
    "aliases": ["18K", "750", "18金", "Au750"],
    "color_variants": ["YG", "WG", "PG", "RG"],
    "density_g_cm3": 15.45,
    "melting_point_c": 905,
    "alloy_components": ["copper", "silver", "palladium", "zinc"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "Japanese mark for 18-karat gold (75% by mass). The dominant bridal-jewelry standard in Japan together with Pt950. International equivalent is the 750 fineness mark. Color variant suffix (YG/WG/PG) typically follows, e.g. K18YG.",
    "see_also": ["K14", "Pt950", "750"],
    "sources": ["Japan Jewelry Association standards", "ISO 9202:2019"]
  },
  {
    "stamp": "K14",
    "metal": "gold",
    "purity": 0.585,
    "fineness": 585,
    "karat": 14,
    "region": ["JP", "US"],
    "aliases": ["14K", "585", "14金", "Au585"],
    "color_variants": ["YG", "WG", "PG", "RG"],
    "density_g_cm3": 13.4,
    "melting_point_c": 882,
    "alloy_components": ["copper", "silver", "zinc", "nickel", "palladium"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "14-karat gold (58.5% by mass). Dominant in US jewelry production. Harder and more durable than K18, more affordable. Slightly less saturated yellow tone in yellow-gold variants.",
    "see_also": ["K18", "K10", "585"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23", "ISO 9202:2019"]
  },
  {
    "stamp": "K10",
    "metal": "gold",
    "purity": 0.417,
    "fineness": 417,
    "karat": 10,
    "region": ["JP", "US"],
    "aliases": ["10K", "417", "10金"],
    "color_variants": ["YG", "WG", "RG"],
    "density_g_cm3": 11.6,
    "melting_point_c": 876,
    "alloy_components": ["copper", "silver", "zinc"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "10-karat gold (41.7%). The minimum legally callable 'gold' in the US per FTC Jewelry Guides. Common in fashion jewelry, class rings, and budget bridal lines.",
    "see_also": ["K14", "K9", "417"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.4"]
  },
  {
    "stamp": "K9",
    "metal": "gold",
    "purity": 0.375,
    "fineness": 375,
    "karat": 9,
    "region": ["UK", "AU", "NZ", "IE"],
    "aliases": ["9K", "375", "9ct"],
    "color_variants": ["YG", "WG", "RG"],
    "density_g_cm3": 11.1,
    "melting_point_c": 880,
    "alloy_components": ["copper", "silver", "zinc"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "9-karat gold (37.5%). Minimum legally callable 'gold' in the UK, Republic of Ireland, Australia, and New Zealand. Below the US 10K minimum, so it cannot be sold as 'gold' in the US.",
    "see_also": ["K10", "375"],
    "sources": ["UK Hallmarking Act 1973", "Birmingham Assay Office reference"]
  },
  {
    "stamp": "999",
    "metal": "gold",
    "purity": 0.999,
    "fineness": 999,
    "karat": 24,
    "region": ["international"],
    "aliases": ["999.9", ".999", "PURE", "K24", "FINE GOLD"],
    "color_variants": ["YG"],
    "density_g_cm3": 19.32,
    "melting_point_c": 1064,
    "alloy_components": [],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q897",
    "notes": "Fineness mark for pure 24-karat gold. Used internationally on bullion and pure-gold jewelry. Disambiguate by context: '999' on silver indicates fine silver, not gold.",
    "see_also": ["K24", "995"],
    "sources": ["ISO 9202:2019"]
  },
  {
    "stamp": "995",
    "metal": "gold",
    "purity": 0.995,
    "fineness": 995,
    "karat": null,
    "region": ["international"],
    "aliases": ["99.5", ".995"],
    "color_variants": ["YG"],
    "density_g_cm3": 19.26,
    "melting_point_c": 1064,
    "alloy_components": ["trace"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "99.5% gold. LBMA Good Delivery minimum for investment-grade gold bars. Sometimes appears on Chinese gold jewelry alongside the 'Chuk Kam' (足金) designation.",
    "see_also": ["999"],
    "sources": ["LBMA Good Delivery Rules"]
  },
  {
    "stamp": "990",
    "metal": "gold",
    "purity": 0.990,
    "fineness": 990,
    "karat": null,
    "region": ["CN", "HK"],
    "aliases": ["99", "Chuk Kam"],
    "color_variants": ["YG"],
    "density_g_cm3": 19.21,
    "melting_point_c": 1064,
    "alloy_components": ["trace"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "99.0% gold. Common in Hong Kong and Mainland China bridal jewelry; the 'Chuk Kam' (足金, 'sufficient gold') designation historically refers to ≥99% gold.",
    "see_also": ["995", "999"],
    "sources": ["Hong Kong Trade Descriptions Ordinance Cap. 362"]
  },
  {
    "stamp": "916",
    "metal": "gold",
    "purity": 0.916,
    "fineness": 916,
    "karat": 22,
    "region": ["IN", "ME", "international"],
    "aliases": ["22K", "K22", "22ct", "916.7"],
    "color_variants": ["YG"],
    "density_g_cm3": 17.7,
    "melting_point_c": 977,
    "alloy_components": ["copper", "silver"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1972095",
    "notes": "22-karat gold fineness (technically 91.67%, rounded to 916). Standard for Indian and Gulf-region bridal jewelry. Coexists with the BIS hallmark in modern Indian production.",
    "see_also": ["K22", "BIS_HALLMARK"],
    "sources": ["Bureau of Indian Standards IS 1417", "Dubai Central Laboratory"]
  },
  {
    "stamp": "875",
    "metal": "gold",
    "purity": 0.875,
    "fineness": 875,
    "karat": 21,
    "region": ["ME"],
    "aliases": ["21K", "21ct"],
    "color_variants": ["YG"],
    "density_g_cm3": 17.0,
    "melting_point_c": 970,
    "alloy_components": ["copper", "silver"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "21-karat gold (87.5%). Standard in Saudi Arabia, UAE, Egypt, and broader Gulf region. Compromise between K22 softness and K18 alloy-feel.",
    "see_also": ["916", "K18"],
    "sources": ["Dubai Central Laboratory"]
  },
  {
    "stamp": "833",
    "metal": "gold",
    "purity": 0.833,
    "fineness": 833,
    "karat": 20,
    "region": ["JP", "FI", "international"],
    "aliases": ["20K", "K20"],
    "color_variants": ["YG"],
    "density_g_cm3": 16.5,
    "melting_point_c": 1010,
    "alloy_components": ["copper", "silver"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "20-karat gold fineness. Uncommon outside Japan and Finland; historically used in select European pieces.",
    "see_also": ["K20"],
    "sources": []
  },
  {
    "stamp": "800",
    "metal": "gold",
    "purity": 0.800,
    "fineness": 800,
    "karat": null,
    "region": ["AT", "DE-historic"],
    "aliases": [],
    "color_variants": ["YG"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "80% gold fineness. Historical Austrian standard; rare. NOT to be confused with the 800 silver standard (continental European silver).",
    "see_also": ["750"],
    "sources": []
  },
  {
    "stamp": "750",
    "metal": "gold",
    "purity": 0.750,
    "fineness": 750,
    "karat": 18,
    "region": ["EU", "international"],
    "aliases": ["18K", "K18", "750 ‰", ".750", "Au750"],
    "color_variants": ["YG", "WG", "RG", "PG"],
    "density_g_cm3": 15.45,
    "melting_point_c": 905,
    "alloy_components": ["copper", "silver", "palladium", "zinc", "nickel"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "18-karat gold fineness. Standard European and Italian jewelry mark. The most common premium gold purity worldwide for fine jewelry.",
    "see_also": ["K18", "585"],
    "sources": ["ISO 9202:2019", "Italian Decreto Legislativo 251/1999"]
  },
  {
    "stamp": "625",
    "metal": "gold",
    "purity": 0.625,
    "fineness": 625,
    "karat": 15,
    "region": ["UK-historic"],
    "aliases": ["15ct", "15K"],
    "color_variants": ["YG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "15-karat gold (62.5%). Legal in the UK only between 1854 and 1932; useful for dating antique British jewelry. Replaced by streamlined 9/14/18/22 karat options under 1932 reform.",
    "see_also": ["750", "375"],
    "sources": ["UK Hallmarking historical regulations 1854-1932"]
  },
  {
    "stamp": "585",
    "metal": "gold",
    "purity": 0.585,
    "fineness": 585,
    "karat": 14,
    "region": ["EU", "international"],
    "aliases": ["14K", "K14", ".585", "Au585"],
    "color_variants": ["YG", "WG", "RG", "PG"],
    "density_g_cm3": 13.4,
    "melting_point_c": 882,
    "alloy_components": ["copper", "silver", "zinc", "nickel", "palladium"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "14-karat gold fineness (58.5%). Standard European mark; equivalent to US 14K. Most common gold purity by volume in the US market.",
    "see_also": ["K14", "583"],
    "sources": ["ISO 9202:2019"]
  },
  {
    "stamp": "583",
    "metal": "gold",
    "purity": 0.583,
    "fineness": 583,
    "karat": 14,
    "region": ["RU", "SU"],
    "aliases": ["14K (Soviet)"],
    "color_variants": ["YG", "RG"],
    "iso_reference": "Russian Federation Order 643 (legacy)",
    "wikidata_qid": null,
    "notes": "Older Russian/Soviet fineness mark for 14-karat gold. The slight (0.2%) difference from the modern 585 standard is real and reflects pre-1994 Soviet gold-content rounding. Distinctive of pre-1994 Soviet jewelry — useful for dating.",
    "see_also": ["585"],
    "sources": ["Soviet gold standards (legacy)"]
  },
  {
    "stamp": "500",
    "metal": "gold",
    "purity": 0.500,
    "fineness": 500,
    "karat": 12,
    "region": ["RU-historic", "international"],
    "aliases": ["12K"],
    "color_variants": ["YG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "12-karat gold (50%). Uncommon in modern jewelry; appears in some gold-filled assemblies and in older Russian production.",
    "see_also": ["417"],
    "sources": []
  },
  {
    "stamp": "417",
    "metal": "gold",
    "purity": 0.417,
    "fineness": 417,
    "karat": 10,
    "region": ["US", "international"],
    "aliases": ["10K", "K10", ".417"],
    "color_variants": ["YG", "WG", "RG"],
    "density_g_cm3": 11.6,
    "melting_point_c": 876,
    "alloy_components": ["copper", "silver", "zinc"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "10-karat gold fineness (41.67%). The minimum legally callable 'gold' in the US per FTC Jewelry Guides.",
    "see_also": ["K10", "375"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23"]
  },
  {
    "stamp": "416",
    "metal": "gold",
    "purity": 0.416,
    "fineness": 416,
    "karat": 10,
    "region": ["US-historic"],
    "aliases": ["10K (legacy)"],
    "color_variants": ["YG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Pre-modern rounding of 10-karat gold. May appear on older US jewelry. Equivalent to current 417 for valuation purposes.",
    "see_also": ["417"],
    "sources": []
  },
  {
    "stamp": "375",
    "metal": "gold",
    "purity": 0.375,
    "fineness": 375,
    "karat": 9,
    "region": ["UK", "AU", "NZ", "IE"],
    "aliases": ["9ct", "9K", "K9", ".375"],
    "color_variants": ["YG", "WG", "RG"],
    "density_g_cm3": 11.1,
    "melting_point_c": 880,
    "alloy_components": ["copper", "silver", "zinc"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "9-karat gold fineness (37.5%). Minimum legal 'gold' in the UK and Commonwealth. Below US 10K minimum so it cannot be sold as 'gold' in the US.",
    "see_also": ["K9"],
    "sources": ["UK Hallmarking Act 1973"]
  },
  {
    "stamp": "333",
    "metal": "gold",
    "purity": 0.333,
    "fineness": 333,
    "karat": 8,
    "region": ["DE", "AT"],
    "aliases": ["8K", "8ct"],
    "color_variants": ["YG"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "8-karat gold (33.3%). Legal in Germany, Austria, and parts of Europe. Not legal as 'gold' in the US or UK.",
    "see_also": ["375"],
    "sources": ["German Punzierungsgesetz 1971"]
  },
  {
    "stamp": "Pt1000",
    "metal": "platinum",
    "purity": 1.000,
    "fineness": 1000,
    "region": ["JP", "international"],
    "aliases": ["PT1000", "Pt", "PLATINUM", "Pt999"],
    "density_g_cm3": 21.45,
    "melting_point_c": 1768,
    "alloy_components": [],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "Pure platinum (99.9%+ by mass). Used on bars and rare bridal pieces. Extremely soft; rarely used for jewelry with wear demands.",
    "see_also": ["Pt950"],
    "sources": ["ISO 9202:2019"]
  },
  {
    "stamp": "Pt950",
    "metal": "platinum",
    "purity": 0.950,
    "fineness": 950,
    "region": ["JP", "international"],
    "aliases": ["PT950", "950Pt", "Plat950", "950"],
    "density_g_cm3": 20.7,
    "melting_point_c": 1755,
    "alloy_components": ["ruthenium", "iridium", "cobalt", "copper", "palladium"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "95% platinum. The most common platinum purity in Japanese bridal jewelry and US engagement rings. Alloying metals vary by manufacturer and intended hardness/casting properties.",
    "see_also": ["Pt900", "K18"],
    "sources": ["Platinum Guild International specifications", "ISO 9202:2019"]
  },
  {
    "stamp": "Pt900",
    "metal": "platinum",
    "purity": 0.900,
    "fineness": 900,
    "region": ["JP", "international"],
    "aliases": ["PT900", "900Pt", "Plat900"],
    "density_g_cm3": 20.1,
    "melting_point_c": 1745,
    "alloy_components": ["iridium", "ruthenium", "palladium", "copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "90% platinum. Common in Japanese bridal jewelry as a slightly more affordable alternative to Pt950, and in US production where harder alloys are preferred for prong durability.",
    "see_also": ["Pt950", "Pt850"],
    "sources": ["Platinum Guild International specifications"]
  },
  {
    "stamp": "Pt850",
    "metal": "platinum",
    "purity": 0.850,
    "fineness": 850,
    "region": ["JP", "international"],
    "aliases": ["PT850", "850Pt"],
    "density_g_cm3": 19.4,
    "melting_point_c": 1730,
    "alloy_components": ["copper", "cobalt", "iridium"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "85% platinum. Used in chains and pieces where strength matters more than purity. The minimum platinum content for which the 'platinum' designation is permitted in the US under FTC guides.",
    "see_also": ["Pt900"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.7"]
  },
  {
    "stamp": "Pt500",
    "metal": "platinum",
    "purity": 0.500,
    "fineness": 500,
    "region": ["JP"],
    "aliases": ["PT500", "500Pt"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "50% platinum. Rare in fine jewelry; sometimes appears in fashion pieces or as alloy backing.",
    "see_also": ["Pt850"],
    "sources": []
  },
  {
    "stamp": "Pd950",
    "metal": "palladium",
    "purity": 0.950,
    "fineness": 950,
    "region": ["international"],
    "aliases": ["PD950", "Pd"],
    "density_g_cm3": 12.0,
    "melting_point_c": 1555,
    "alloy_components": ["ruthenium", "copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1278",
    "notes": "95% palladium. White-metal alternative to platinum; ~40% lighter, more affordable, and hypoallergenic. UK introduced hallmarking for palladium in 2010.",
    "see_also": ["Pt950"],
    "sources": ["UK Hallmarking Act 1973 (palladium amendment 2010)"]
  },
  {
    "stamp": "Pd500",
    "metal": "palladium",
    "purity": 0.500,
    "fineness": 500,
    "region": ["international"],
    "aliases": ["PD500"],
    "density_g_cm3": null,
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1278",
    "notes": "50% palladium. Uncommon; usually appears in palladium-silver alloys for medical or industrial use rather than jewelry.",
    "see_also": ["Pd950"],
    "sources": []
  },
  {
    "stamp": "STERLING",
    "metal": "silver",
    "purity": 0.925,
    "fineness": 925,
    "region": ["US", "UK"],
    "aliases": ["STERLING 925", "925", "SILVER 925", ".925", "S925", "STERL"],
    "density_g_cm3": 10.36,
    "melting_point_c": 893,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q220517",
    "notes": "US/UK sterling silver mark. The word 'STERLING' alone is legally equivalent to 925 fineness in the US (FTC Jewelry Guides) and equivalent to the lion passant mark in the UK post-1300.",
    "see_also": ["925", "SILVER 925", "LION_PASSANT"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.6", "UK Hallmarking Act 1973"]
  },
  {
    "stamp": "925",
    "metal": "silver",
    "purity": 0.925,
    "fineness": 925,
    "region": ["international"],
    "aliases": ["STERLING", "STERLING 925", "SILVER 925", ".925", "S925", "SV925"],
    "density_g_cm3": 10.36,
    "melting_point_c": 893,
    "alloy_components": ["copper", "germanium"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q220517",
    "notes": "International fineness mark for sterling silver (92.5%). The global standard for silver jewelry. Some modern alloys substitute germanium for part of the copper content to reduce tarnish (e.g., Argentium sterling).",
    "see_also": ["STERLING", "SILVER 925", "SV925"],
    "sources": ["ISO 9202:2019"]
  },
  {
    "stamp": "SILVER 925",
    "metal": "silver",
    "purity": 0.925,
    "fineness": 925,
    "region": ["JP", "international"],
    "aliases": ["925", "SV925", "STERLING", "STERLING 925", ".925", "S925"],
    "density_g_cm3": 10.36,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q220517",
    "notes": "Most common Japanese-domestic style of sterling silver hallmark. Equivalent in meaning to STERLING / .925 / SV925.",
    "see_also": ["925", "SV925"],
    "sources": ["Japan Jewelry Association standards"]
  },
  {
    "stamp": "SV925",
    "metal": "silver",
    "purity": 0.925,
    "fineness": 925,
    "region": ["JP"],
    "aliases": ["SILVER 925", "925", "STERLING"],
    "density_g_cm3": 10.36,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q220517",
    "notes": "Japanese-style sterling silver hallmark. The 'SV' is an abbreviation of 'silver' standard in Japanese jewelry trade.",
    "see_also": ["SILVER 925"],
    "sources": []
  },
  {
    "stamp": "999",
    "metal": "silver",
    "purity": 0.999,
    "fineness": 999,
    "region": ["international"],
    "aliases": ["FINE SILVER", ".999", "999 SILVER"],
    "density_g_cm3": 10.49,
    "melting_point_c": 961,
    "alloy_components": [],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1090",
    "notes": "Fine silver (99.9%). Too soft for most wearable jewelry; used for bullion, fused-silver art jewelry, and some Eastern bridal pieces. Disambiguate from 999 gold by metal context.",
    "see_also": ["925"],
    "sources": ["LBMA Good Delivery Rules"]
  },
  {
    "stamp": "958",
    "metal": "silver",
    "purity": 0.958,
    "fineness": 958,
    "region": ["UK"],
    "aliases": ["BRITANNIA", "BRITANNIA SILVER", ".958"],
    "density_g_cm3": 10.4,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q865987",
    "notes": "Britannia silver (95.84%). Higher purity than sterling. Mandatory UK standard 1697-1720 to prevent clipping of silver coinage; optional since then.",
    "see_also": ["STERLING", "BRITANNIA"],
    "sources": ["UK Wrought Plate Act 1697"]
  },
  {
    "stamp": "950",
    "metal": "silver",
    "purity": 0.950,
    "fineness": 950,
    "region": ["FR"],
    "aliases": ["FRENCH 1ST STANDARD", "Minerva head"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "French first standard silver (95%). Marked with the Minerva head poinçon. Higher than sterling; used by French silversmiths historically.",
    "see_also": ["800", "SILVER 925"],
    "sources": ["French Code Général des Impôts (poinçons de garantie)"]
  },
  {
    "stamp": "900",
    "metal": "silver",
    "purity": 0.900,
    "fineness": 900,
    "region": ["US", "FR-historic"],
    "aliases": ["COIN SILVER", "FRENCH 2ND STANDARD"],
    "density_g_cm3": 10.3,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "Coin silver / French 2nd standard (90%). Historical US silver standard melted from coins. Common in 19th-century American flatware and southern US jewelry.",
    "see_also": ["STERLING", "925"],
    "sources": []
  },
  {
    "stamp": "875",
    "metal": "silver",
    "purity": 0.875,
    "fineness": 875,
    "region": ["RU", "SU"],
    "aliases": ["SOVIET SILVER"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "87.5% silver fineness. Soviet-era standard, often paired with the 'kokoshnik' woman's head poinçon. Useful for dating Russian/Soviet flatware and jewelry to the post-1958 period.",
    "see_also": ["835", "925"],
    "sources": []
  },
  {
    "stamp": "835",
    "metal": "silver",
    "purity": 0.835,
    "fineness": 835,
    "region": ["DE", "AT", "NL", "EU"],
    "aliases": ["GERMAN SILVER STANDARD"],
    "density_g_cm3": 10.2,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "Continental European silver standard (83.5%). Common in German, Dutch, Austrian, and Scandinavian pieces. Often stamped alongside national assay marks.",
    "see_also": ["800"],
    "sources": ["German Punzierungsgesetz 1888 (legacy)"]
  },
  {
    "stamp": "800",
    "metal": "silver",
    "purity": 0.800,
    "fineness": 800,
    "region": ["DE", "IT", "EU"],
    "aliases": ["CONTINENTAL SILVER"],
    "density_g_cm3": 10.1,
    "alloy_components": ["copper"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": null,
    "notes": "European silver standard (80%). Common in older German, Italian, and Eastern European silverware and jewelry. Sometimes stamped with a crescent moon and crown (German national mark).",
    "see_also": ["835", "925"],
    "sources": ["German Punzierungsgesetz"]
  },
  {
    "stamp": "GP",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["GOLD PLATED", "G.P."],
    "iso_reference": "ISO 4523",
    "wikidata_qid": "Q899605",
    "notes": "Gold plated. A surface gold layer typically <0.5 microns (or by ISO 4523, anything below gold-filled threshold). Limited intrinsic gold value (typically <1% by weight).",
    "see_also": ["GEP", "GF"],
    "sources": ["ISO 4523:2009"]
  },
  {
    "stamp": "GEP",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["GOLD ELECTROPLATED", "G.E.P."],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Gold electroplated. Plating applied via electrolysis. Per FTC, requires minimum thickness equivalent to 7 millionths of an inch of fine gold. Often paired with karat: '14K GEP'.",
    "see_also": ["GP", "HGE"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "HGE",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["HEAVY GOLD ELECTROPLATE", "HGP"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Heavy gold electroplate. Per FTC, plating ≥100 millionths of an inch (~2.5 microns) thick. Still surface coating, not solid gold.",
    "see_also": ["GEP", "GF"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "GF",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["US", "international"],
    "aliases": ["GOLD FILLED", "G.F."],
    "iso_reference": null,
    "wikidata_qid": "Q5577717",
    "notes": "Gold filled. Bonded gold layer making up at least 1/20 (5%) of total weight per FTC standards. Far more durable than gold plating; lifespan in normal wear comparable to solid karat gold.",
    "see_also": ["RGP", "1/20 14K GF"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "1/20 14K GF",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["14/20 GF", "14K GF", "1/20 14kt GF"],
    "iso_reference": null,
    "wikidata_qid": "Q5577717",
    "notes": "Gold filled with a 14K layer making up 1/20 (5%) of total weight. Common quality standard for affordable jewelry with real gold surface.",
    "see_also": ["GF"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "1/10 12K GF",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["12K GF", "1/10 12kt GF"],
    "iso_reference": null,
    "wikidata_qid": "Q5577717",
    "notes": "Gold filled with 12K layer making up 1/10 (10%) of total weight. Higher gold content than typical 1/20 GF; common on older American costume pieces.",
    "see_also": ["GF"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "RGP",
    "metal": "gold-rolled",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["ROLLED GOLD PLATE", "R.G.P."],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Rolled gold plate. Similar to gold filled but with a thinner bonded layer (less than 1/20 by weight). More durable than electroplate, less than gold filled.",
    "see_also": ["GF", "GP"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "GR",
    "metal": "gold-rolled",
    "purity": null,
    "fineness": null,
    "region": ["FR", "international"],
    "aliases": ["GOLD ROLLED", "PLAQUÉ OR"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "European equivalent of rolled gold plate / gold filled. The French 'plaqué or' designation has specific minimum micron thickness requirements (varying by era).",
    "see_also": ["RGP", "GF"],
    "sources": []
  },
  {
    "stamp": "VERMEIL",
    "metal": "silver-gilt",
    "purity": 0.925,
    "fineness": 925,
    "region": ["international", "FR"],
    "aliases": ["GOLD VERMEIL", "SILVER VERMEIL"],
    "iso_reference": null,
    "wikidata_qid": "Q3556099",
    "notes": "Sterling silver base with gold plating of at least 2.5 microns thickness and at least 10K gold per FTC standards. Premium alternative to gold plating with real precious-metal substrate.",
    "see_also": ["SILVER 925", "GP"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "TI",
    "metal": "titanium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["TITANIUM", "Ti"],
    "density_g_cm3": 4.51,
    "melting_point_c": 1668,
    "alloy_components": ["aluminum", "vanadium"],
    "iso_reference": null,
    "wikidata_qid": "Q716",
    "notes": "Titanium. Lightweight (45% of steel), hypoallergenic, scratch-resistant. Common in modern wedding bands and watch cases. Cannot be soldered conventionally; sizing is restricted.",
    "see_also": ["TUNGSTEN", "ZIRCONIUM"],
    "sources": []
  },
  {
    "stamp": "TUNGSTEN",
    "metal": "tungsten-carbide",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["TUNGSTEN CARBIDE", "WC"],
    "density_g_cm3": 15.6,
    "melting_point_c": 2870,
    "alloy_components": ["carbon", "nickel binder", "cobalt binder"],
    "iso_reference": null,
    "wikidata_qid": "Q207552",
    "notes": "Tungsten carbide. Mohs 8.5-9; extremely scratch-resistant. Common in modern men's wedding bands. Brittle — can shatter on hard impact. Cannot be resized (must be replaced).",
    "see_also": ["TI", "CERAMIC"],
    "sources": []
  },
  {
    "stamp": "ZIRCONIUM",
    "metal": "zirconium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["BLACK ZIRCONIUM", "Zr"],
    "density_g_cm3": 6.52,
    "melting_point_c": 1855,
    "alloy_components": [],
    "iso_reference": null,
    "wikidata_qid": "Q706",
    "notes": "Zirconium. When heat-treated, surface oxidizes to a hard ceramic black layer ('black zirconium' rings). Hypoallergenic, lightweight, scratch-resistant.",
    "see_also": ["TI"],
    "sources": []
  },
  {
    "stamp": "CERAMIC",
    "metal": "ceramic",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["TECHNICAL CERAMIC"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Technical/zirconia ceramic. Mohs 8.5+, extremely scratch-resistant, hypoallergenic. Cannot be resized. Common in watch bezels and contemporary rings.",
    "see_also": ["TUNGSTEN"],
    "sources": []
  },
  {
    "stamp": "RHODIUM PLATED",
    "metal": "rhodium-plated",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["RHODIUM", "RH PLATED"],
    "iso_reference": null,
    "wikidata_qid": "Q1849",
    "notes": "Rhodium plating. Common over white gold to enhance whiteness and reduce yellow undertone. Plating typically 0.75-1 micron; wears off over 1-3 years requiring re-plating. Sometimes used over silver to inhibit tarnish.",
    "see_also": ["WG"],
    "sources": []
  },
  {
    "stamp": "LION_PASSANT",
    "metal": "silver",
    "purity": 0.925,
    "fineness": 925,
    "region": ["UK"],
    "aliases": ["LION", "Lion Passant", "WALKING LION"],
    "iso_reference": null,
    "wikidata_qid": "Q1265834",
    "notes": "British assay mark: walking lion in profile. Indicates sterling silver (925) since 1544. One of the four mandatory British hallmarks (sponsor + standard + assay office + date letter). After 1822 the lion's head changes from facing forward to in-profile.",
    "see_also": ["STERLING", "BRITANNIA", "LEOPARDS_HEAD"],
    "sources": ["UK Hallmarking Act 1973", "Birmingham Assay Office historical reference"]
  },
  {
    "stamp": "BRITANNIA",
    "metal": "silver",
    "purity": 0.958,
    "fineness": 958,
    "region": ["UK"],
    "aliases": ["Britannia mark", "SEATED BRITANNIA"],
    "iso_reference": null,
    "wikidata_qid": "Q865987",
    "notes": "British assay mark: seated figure of Britannia with shield and spear. Indicates Britannia silver (958, higher than sterling). Mandatory 1697-1720, then optional. Often paired with lion's head erased.",
    "see_also": ["LION_PASSANT", "958"],
    "sources": ["UK Wrought Plate Act 1697"]
  },
  {
    "stamp": "LIONS_HEAD_ERASED",
    "metal": "silver",
    "purity": 0.958,
    "fineness": 958,
    "region": ["UK"],
    "aliases": ["Lion's head erased"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay mark: lion's head 'erased' (severed with jagged base). Paired with Britannia figure to mark Britannia silver. Used 1697-1720 mandatorily.",
    "see_also": ["BRITANNIA"],
    "sources": []
  },
  {
    "stamp": "CROWN",
    "metal": "gold",
    "purity": null,
    "fineness": null,
    "region": ["UK"],
    "aliases": ["Crown mark"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay mark: crown symbol indicates gold (used 1798-1974). Specific karat shown alongside. Replaced by fineness numbers as standard mark in 1975.",
    "see_also": ["750", "375"],
    "sources": ["UK Hallmarking historical regulations"]
  },
  {
    "stamp": "ANCHOR",
    "metal": "assay-mark",
    "purity": null,
    "fineness": null,
    "region": ["UK"],
    "aliases": ["Birmingham Anchor"],
    "iso_reference": null,
    "wikidata_qid": "Q4866015",
    "notes": "British assay office mark: anchor symbol indicates Birmingham Assay Office (established 1773 by Act of Parliament). Found alongside purity mark and date letter. Birmingham was historically the largest assay office by volume.",
    "see_also": ["LEOPARDS_HEAD", "CASTLE"],
    "sources": ["Birmingham Assay Office historical records"]
  },
  {
    "stamp": "LEOPARDS_HEAD",
    "metal": "assay-mark",
    "purity": null,
    "fineness": null,
    "region": ["UK"],
    "aliases": ["Leopard's Head", "London Mark"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay office mark: leopard's head (crowned 1478-1821, uncrowned after) indicates London Assay Office (Goldsmiths' Hall, established 1300). Among the oldest hallmarks in continuous use.",
    "see_also": ["ANCHOR", "CASTLE"],
    "sources": ["Goldsmiths' Company historical records"]
  },
  {
    "stamp": "CASTLE",
    "metal": "assay-mark",
    "purity": null,
    "fineness": null,
    "region": ["UK"],
    "aliases": ["Edinburgh Castle", "THREE TOWER CASTLE"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay office mark: three-towered castle indicates Edinburgh Assay Office (Scotland, established 1457). Used continuously since the 15th century.",
    "see_also": ["ANCHOR", "LEOPARDS_HEAD"],
    "sources": ["Edinburgh Assay Office records"]
  },
  {
    "stamp": "ROSE",
    "metal": "assay-mark",
    "purity": null,
    "fineness": null,
    "region": ["UK"],
    "aliases": ["Sheffield Rose", "TUDOR ROSE"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay office mark: Tudor rose indicates Sheffield Assay Office (established 1773 by the same Act as Birmingham, traded the crown mark on gold for the rose only in 1975). Sheffield historically specialized in silver.",
    "see_also": ["ANCHOR"],
    "sources": ["Sheffield Assay Office records"]
  },
  {
    "stamp": "THREE_WHEATSHEAVES",
    "metal": "assay-mark",
    "purity": null,
    "fineness": null,
    "region": ["UK-historic"],
    "aliases": ["Chester wheatsheaves", "CHESTER"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "British assay office mark: three wheatsheaves (sometimes with a sword) indicates Chester Assay Office. Operated 1701-1962, then closed. Useful for dating earlier 20th-century British jewelry as a closed-office mark.",
    "see_also": ["LEOPARDS_HEAD"],
    "sources": ["Chester Assay Office historical records"]
  },
  {
    "stamp": "JIS_HALLMARK",
    "metal": "verified",
    "purity": null,
    "fineness": null,
    "region": ["JP"],
    "aliases": ["造幣局ホールマーク", "Japan Mint Hallmark", "HINSHITSU MARK"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Japanese government hallmark issued by the Japan Mint (造幣局, Zōheikyoku). Optional but prestigious; certifies metal purity as stamped. Look for the chrysanthemum-and-balance symbol next to the purity mark. Introduced 1929.",
    "see_also": ["K18", "Pt950"],
    "sources": ["Japan Mint (Zōheikyoku) public records"]
  },
  {
    "stamp": "BIS_HALLMARK",
    "metal": "verified",
    "purity": null,
    "fineness": null,
    "region": ["IN"],
    "aliases": ["Bureau of Indian Standards mark", "BIS"],
    "iso_reference": "IS 1417",
    "wikidata_qid": "Q866935",
    "notes": "Indian government hallmark from the Bureau of Indian Standards. Mandatory for all gold jewelry in India since June 2021 (HUID system). Includes BIS logo, fineness, jeweler ID, and HUID code.",
    "see_also": ["916", "K22"],
    "sources": ["Bureau of Indian Standards IS 1417"]
  },
  {
    "stamp": "MINERVA_HEAD",
    "metal": "verified",
    "purity": 0.950,
    "fineness": 950,
    "region": ["FR"],
    "aliases": ["TÊTE DE MINERVE", "French first standard"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "French poinçon: Minerva head indicates 950 silver (first standard). Used since 1838. Number 1 next to head = first standard (950), number 2 = second standard (800).",
    "see_also": ["950", "800"],
    "sources": ["French Code Général des Impôts"]
  },
  {
    "stamp": "EAGLE_HEAD",
    "metal": "verified",
    "purity": 0.750,
    "fineness": 750,
    "region": ["FR"],
    "aliases": ["TÊTE D'AIGLE", "French gold poinçon"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "French poinçon: eagle head indicates 750 gold (first/finest grade since 1838). Numbered eagle heads (1, 2, 3) indicate finer to coarser grades.",
    "see_also": ["750", "K18"],
    "sources": ["French Code Général des Impôts"]
  },
  {
    "stamp": "KOKOSHNIK",
    "metal": "verified",
    "purity": null,
    "fineness": null,
    "region": ["RU", "SU"],
    "aliases": ["Kokoshnik mark", "Woman's head profile"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Russian/Soviet assay mark: woman's head profile in kokoshnik headdress. Two main eras: facing left (1908-1926) and facing right (1958-1994). Useful for dating Russian jewelry by orientation and accompanying mark.",
    "see_also": ["583", "875"],
    "sources": []
  },
  {
    "stamp": "CCM",
    "metal": "verified",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["Common Control Mark", "CCM"],
    "iso_reference": "Vienna Convention 1972",
    "wikidata_qid": null,
    "notes": "Common Control Mark from the Vienna Convention on Hallmarking. Mutually recognized by signatory countries (UK, Austria, Switzerland, Portugal, Netherlands, Sweden, etc.). Format: balance/scales for the metal type, surrounded by fineness number.",
    "see_also": ["LEOPARDS_HEAD"],
    "sources": ["Vienna Convention on Control of Articles of Precious Metals 1972"]
  },
  {
    "stamp": "WG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["WHITE GOLD", "Or Gris"],
    "iso_reference": null,
    "wikidata_qid": "Q15029",
    "notes": "White gold modifier. Gold alloyed with white metals (palladium, nickel, silver, zinc) to produce white appearance. Almost always rhodium-plated for whiter finish; plating wears in 1-3 years. Combined with karat e.g. K18WG.",
    "see_also": ["YG", "PG", "RHODIUM PLATED"],
    "sources": []
  },
  {
    "stamp": "YG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["YELLOW GOLD", "Or Jaune"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Yellow gold modifier. Standard warm-gold alloy with copper and silver in roughly equal proportion. Combined with karat e.g. K18YG.",
    "see_also": ["WG", "RG"],
    "sources": []
  },
  {
    "stamp": "RG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["ROSE GOLD", "Or Rose", "PG", "PINK GOLD", "RED GOLD"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Rose / pink / red gold modifier. Gold alloyed with higher copper content (and minimal silver) for warm pink to red hue. Combined with karat e.g. K18PG or K18RG.",
    "see_also": ["YG", "WG", "PG"],
    "sources": []
  },
  {
    "stamp": "PG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["JP", "international"],
    "aliases": ["PINK GOLD", "ROSE GOLD", "RG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Pink gold modifier. Standard Japanese term for rose gold. Combined with karat e.g. K18PG. Lighter pink tone than typical Western rose gold due to lower copper proportion.",
    "see_also": ["RG"],
    "sources": []
  },
  {
    "stamp": "GG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["GREEN GOLD", "Or Vert", "ELECTRUM"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Green gold modifier. Gold alloyed with high silver content and no copper for a pale greenish tint. Rare in jewelry; used for artistic effect in multi-color gold pieces. Historically referred to as 'electrum' in antiquity.",
    "see_also": ["YG"],
    "sources": []
  },
  {
    "stamp": "BG",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["BLACK GOLD"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Black gold. Achieved by surface treatment (laser, oxidation, or rhodium-cobalt plating) on gold alloy, not by alloying. Marketing term rather than a metallurgical standard.",
    "see_also": ["WG"],
    "sources": []
  },
  {
    "stamp": "BLUE GOLD",
    "metal": "gold-alloy-modifier",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["AuFe", "AuIn"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Blue gold. Genuinely blue-tinted gold alloy made with iron (Au-Fe) or indium (Au-In). Brittle and limited to surface inlay or accent use. Rare; primarily artistic.",
    "see_also": ["GG"],
    "sources": []
  },
  {
    "stamp": "PURPLE GOLD",
    "metal": "gold-alloy-modifier",
    "purity": 0.75,
    "fineness": 750,
    "region": ["international"],
    "aliases": ["AMETHYST GOLD", "AuAl2"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Purple gold (Au-Al intermetallic compound AuAl2). 79% gold by mass approximately equivalent to 18K. Extremely brittle (cannot be cast as a structural ring), used as inlay or accent stones.",
    "see_also": ["GG", "BLUE GOLD"],
    "sources": []
  },
  {
    "stamp": "EP",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["US-historic"],
    "aliases": ["ELECTROPLATE", "E.P."],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Electroplate. Older US mark for electroplated silver or gold. Without 'gold' or 'silver' prefix, refers to silver-electroplate over base metal.",
    "see_also": ["GEP", "SP"],
    "sources": []
  },
  {
    "stamp": "EPNS",
    "metal": "silver-plated",
    "purity": null,
    "fineness": null,
    "region": ["UK", "international"],
    "aliases": ["ELECTROPLATED NICKEL SILVER", "E.P.N.S."],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Electroplated nickel silver. Silver plating over a nickel-silver (cupronickel-zinc) base. Common on Victorian and Edwardian tableware and costume jewelry. Low intrinsic silver value.",
    "see_also": ["EP", "SP"],
    "sources": []
  },
  {
    "stamp": "SP",
    "metal": "silver-plated",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["SILVER PLATED", "S.P."],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Silver plated. Surface silver layer over base metal (usually copper or nickel alloy). Low intrinsic silver content.",
    "see_also": ["EPNS"],
    "sources": []
  },
  {
    "stamp": "NICKEL SILVER",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["GERMAN SILVER", "ALPACCA", "NEW SILVER"],
    "iso_reference": null,
    "wikidata_qid": "Q381044",
    "notes": "Nickel silver. Despite the name, contains NO silver — alloy of copper, nickel, and zinc. Costume jewelry base metal. Often plated with real silver (see EPNS).",
    "see_also": ["EPNS"],
    "sources": []
  },
  {
    "stamp": "STEEL",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["STAINLESS STEEL", "316L", "SS"],
    "density_g_cm3": 7.98,
    "iso_reference": null,
    "wikidata_qid": "Q11427",
    "notes": "Stainless steel (typically 316L surgical grade in jewelry). Hypoallergenic, durable, low cost. Common in modern men's bands and watches.",
    "see_also": ["TI"],
    "sources": []
  },
  {
    "stamp": "BRASS",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["YELLOW BRASS"],
    "density_g_cm3": 8.4,
    "alloy_components": ["copper", "zinc"],
    "iso_reference": null,
    "wikidata_qid": "Q39782",
    "notes": "Brass. Copper-zinc alloy, yellow appearance. Common base for costume jewelry; sometimes plated with gold. Tarnishes and can cause skin discoloration.",
    "see_also": ["BRONZE"],
    "sources": []
  },
  {
    "stamp": "BRONZE",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": [],
    "density_g_cm3": 8.8,
    "alloy_components": ["copper", "tin"],
    "iso_reference": null,
    "wikidata_qid": "Q34095",
    "notes": "Bronze. Copper-tin alloy, reddish-brown. Historical jewelry material; some modern artisanal use. Patinas over time.",
    "see_also": ["BRASS"],
    "sources": []
  },
  {
    "stamp": "COPPER",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["Cu"],
    "density_g_cm3": 8.96,
    "iso_reference": null,
    "wikidata_qid": "Q753",
    "notes": "Pure copper. Antimicrobial properties; warm reddish color. Causes green skin discoloration on some wearers. Common in Southwest US Native American jewelry.",
    "see_also": ["BRASS", "BRONZE"],
    "sources": []
  },
  {
    "stamp": "Ir",
    "metal": "iridium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["IRIDIUM"],
    "density_g_cm3": 22.56,
    "melting_point_c": 2466,
    "iso_reference": null,
    "wikidata_qid": "Q1828",
    "notes": "Iridium. Densest stable metal. Rare as standalone jewelry; common as alloying element in platinum (Pt-Ir alloy improves hardness).",
    "see_also": ["Pt950"],
    "sources": []
  },
  {
    "stamp": "Rh",
    "metal": "rhodium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["RHODIUM"],
    "density_g_cm3": 12.41,
    "melting_point_c": 1964,
    "iso_reference": null,
    "wikidata_qid": "Q1849",
    "notes": "Rhodium. Bright white, highly reflective. Almost never used as solid metal in jewelry due to cost (often priciest precious metal by weight); used as plating over white gold and silver.",
    "see_also": ["RHODIUM PLATED"],
    "sources": []
  },
  {
    "stamp": "Ru",
    "metal": "ruthenium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["RUTHENIUM"],
    "density_g_cm3": 12.45,
    "melting_point_c": 2334,
    "iso_reference": null,
    "wikidata_qid": "Q1849",
    "notes": "Ruthenium. Alloying element in platinum (Pt-Ru) to improve hardness for prong settings. Rare as standalone jewelry metal.",
    "see_also": ["Pt950"],
    "sources": []
  },
  {
    "stamp": "FILLED",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["FILL", "F"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Abbreviated 'filled' mark, generally indicating gold-filled when paired with karat (e.g., '14K FILLED'). Per US FTC, requires ≥1/20 bonded gold by weight.",
    "see_also": ["GF"],
    "sources": []
  },
  {
    "stamp": "PLATED",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["PLATE", "PL"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Abbreviated 'plated' mark, indicating surface plating. Often paired with karat (e.g., '18K PLATED'). Surface coating only; low intrinsic value.",
    "see_also": ["GP"],
    "sources": []
  },
  {
    "stamp": "PLAQUÉ OR",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["FR"],
    "aliases": ["GOLD ROLLED", "DOUBLÉ OR"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "French gold-filled / rolled-gold designation. Specific micron-thickness requirements vary historically; 'plaqué or G' (garanti) indicates minimum 20-micron bonded gold.",
    "see_also": ["GF", "GR"],
    "sources": ["French jewelry regulations"]
  },
  {
    "stamp": "FIX",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["FR-historic"],
    "aliases": ["FIX OR"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Historical French mark for high-quality gold-filled jewelry produced by the FIX company, mid-20th century. Sometimes confused as a generic mark; actually a brand reference.",
    "see_also": ["PLAQUÉ OR"],
    "sources": []
  },
  {
    "stamp": "GOLDFILL",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["GOLD FILL", "GOLDFILLED"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Single-word variant of 'gold filled' mark. Same FTC standard (≥1/20 bonded gold by weight).",
    "see_also": ["GF"],
    "sources": []
  },
  {
    "stamp": "MICRON",
    "metal": "gold-plated",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["MICRON PLATED", "3 MICRON", "5 MICRON"],
    "iso_reference": "ISO 4523",
    "wikidata_qid": null,
    "notes": "Heavy gold plating measured by micron thickness. '3 micron', '5 micron', etc. indicate plating thickness. 5+ microns approaches vermeil/gold-filled durability.",
    "see_also": ["GP", "VERMEIL"],
    "sources": ["ISO 4523:2009"]
  },
  {
    "stamp": "1000",
    "metal": "platinum",
    "purity": 1.000,
    "fineness": 1000,
    "region": ["international"],
    "aliases": ["Pt1000", "999"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "Pure platinum fineness mark. Disambiguate from gold or silver '1000' by surrounding marks or color.",
    "see_also": ["Pt1000"],
    "sources": []
  },
  {
    "stamp": "999.5",
    "metal": "platinum",
    "purity": 0.9995,
    "fineness": 999,
    "region": ["international"],
    "aliases": ["PT999"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "99.95% platinum. Common bullion-grade designation.",
    "see_also": ["Pt1000"],
    "sources": []
  },
  {
    "stamp": "850",
    "metal": "platinum",
    "purity": 0.850,
    "fineness": 850,
    "region": ["international"],
    "aliases": ["Pt850"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "85% platinum fineness mark. Minimum platinum content allowed under FTC for the 'platinum' designation.",
    "see_also": ["Pt850"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.7"]
  },
  {
    "stamp": "PALLADIUM",
    "metal": "palladium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["Pd"],
    "iso_reference": null,
    "wikidata_qid": "Q1278",
    "notes": "Generic palladium designation when stamped without fineness number. Under FTC, the word 'palladium' alone implies the highest commercially common purity (Pd950 or higher).",
    "see_also": ["Pd950"],
    "sources": []
  },
  {
    "stamp": "Au",
    "metal": "gold",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["GOLD"],
    "iso_reference": null,
    "wikidata_qid": "Q897",
    "notes": "Chemical symbol for gold (Latin: aurum). Often used as prefix to fineness (Au750 = 18K gold).",
    "see_also": ["K18"],
    "sources": []
  },
  {
    "stamp": "Ag",
    "metal": "silver",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["SILVER"],
    "iso_reference": null,
    "wikidata_qid": "Q1090",
    "notes": "Chemical symbol for silver (Latin: argentum). Often used as prefix to fineness (Ag925 = sterling).",
    "see_also": ["925"],
    "sources": []
  },
  {
    "stamp": "Pt",
    "metal": "platinum",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["PLAT", "PLATINUM"],
    "iso_reference": null,
    "wikidata_qid": "Q880",
    "notes": "Chemical symbol for platinum. Often used as prefix to fineness (Pt950, Pt900, etc.).",
    "see_also": ["Pt950"],
    "sources": []
  },
  {
    "stamp": "Pd",
    "metal": "palladium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["PALLADIUM"],
    "iso_reference": null,
    "wikidata_qid": "Q1278",
    "notes": "Chemical symbol for palladium. Often used as prefix to fineness (Pd950, Pd500).",
    "see_also": ["Pd950"],
    "sources": []
  },
  {
    "stamp": "583",
    "metal": "gold",
    "purity": 0.583,
    "fineness": 583,
    "karat": 14,
    "region": ["SU-historic", "RU"],
    "aliases": ["583 пробы"],
    "color_variants": ["YG", "RG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Older Soviet 14K gold standard. Distinct from modern 585 by 0.2% (actual measured difference, not rounding). Pre-1994 dating mark for Russian jewelry.",
    "see_also": ["585"],
    "sources": []
  },
  {
    "stamp": ".999",
    "metal": "silver",
    "purity": 0.999,
    "fineness": 999,
    "region": ["US"],
    "aliases": ["999", "FINE SILVER"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q1090",
    "notes": "Dotted-prefix American convention for fine silver fineness. The dot prefix distinguishes the fineness number from karat (e.g., '925' could be misread as a model number).",
    "see_also": ["925"],
    "sources": []
  },
  {
    "stamp": "999.9",
    "metal": "gold",
    "purity": 0.9999,
    "fineness": 999,
    "karat": 24,
    "region": ["international"],
    "aliases": ["FOUR NINES"],
    "iso_reference": "LBMA",
    "wikidata_qid": "Q897",
    "notes": "99.99% gold ('four nines'). LBMA Good Delivery and Royal Canadian Mint bullion standard. Higher purity than the 999.5/999 minimum.",
    "see_also": ["999", "K24"],
    "sources": ["LBMA Good Delivery Rules", "Royal Canadian Mint specifications"]
  },
  {
    "stamp": "750‰",
    "metal": "gold",
    "purity": 0.750,
    "fineness": 750,
    "karat": 18,
    "region": ["EU"],
    "aliases": ["750", "K18"],
    "color_variants": ["YG", "WG", "RG"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "Per-mille (‰) variant of the 750 mark, common in Continental European stamps.",
    "see_also": ["750"],
    "sources": []
  },
  {
    "stamp": "750/1000",
    "metal": "gold",
    "purity": 0.750,
    "fineness": 750,
    "karat": 18,
    "region": ["EU"],
    "aliases": ["750", "K18"],
    "color_variants": ["YG", "WG", "RG"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q21039",
    "notes": "Fraction-form variant of the 750 fineness mark, used in some European national markings.",
    "see_also": ["750"],
    "sources": []
  },
  {
    "stamp": "950Pt",
    "metal": "platinum",
    "purity": 0.950,
    "fineness": 950,
    "region": ["international"],
    "aliases": ["Pt950", "PT950"],
    "iso_reference": "ISO 9202",
    "wikidata_qid": "Q880",
    "notes": "Fineness-first variant of the Pt950 mark; meaning identical.",
    "see_also": ["Pt950"],
    "sources": []
  },
  {
    "stamp": "1/30",
    "metal": "gold-filled",
    "purity": null,
    "fineness": null,
    "region": ["US"],
    "aliases": ["1/30 GF"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Gold layer making up 1/30 of total weight (3.33%). Lower-end gold-filled standard, often on chain stock. Less durable than 1/20 standard.",
    "see_also": ["GF"],
    "sources": ["FTC Jewelry Guide 16 CFR Part 23.5"]
  },
  {
    "stamp": "MOKUME-GANE",
    "metal": "mixed-metal",
    "purity": null,
    "fineness": null,
    "region": ["JP", "international"],
    "aliases": ["木目金", "WOODGRAIN METAL"],
    "iso_reference": null,
    "wikidata_qid": "Q635011",
    "notes": "Japanese mixed-metal forging technique. Layered gold, silver, copper, and shakudo billets forged and cut to reveal wood-grain pattern. Pieces typically carry the metallurgist's mark plus a hallmark for the highest-purity component metal.",
    "see_also": ["SHAKUDO"],
    "sources": ["Japan Mokume-Gane Association"]
  },
  {
    "stamp": "SHAKUDO",
    "metal": "mixed-metal",
    "purity": null,
    "fineness": null,
    "region": ["JP"],
    "aliases": ["赤銅"],
    "alloy_components": ["copper", "gold"],
    "iso_reference": null,
    "wikidata_qid": "Q3475929",
    "notes": "Japanese copper-gold alloy (~4-10% gold). Develops a deep blue-black patina via traditional Niiro chemical treatment. Used in sword fittings and contemporary jewelry.",
    "see_also": ["MOKUME-GANE", "SHIBUICHI"],
    "sources": []
  },
  {
    "stamp": "SHIBUICHI",
    "metal": "mixed-metal",
    "purity": null,
    "fineness": null,
    "region": ["JP"],
    "aliases": ["四分一"],
    "alloy_components": ["copper", "silver"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Japanese copper-silver alloy (typically 75% Cu / 25% Ag, hence the name 'one fourth'). Develops grayish patina; used in mokume-gane layering and standalone pieces.",
    "see_also": ["MOKUME-GANE", "SHAKUDO"],
    "sources": []
  },
  {
    "stamp": "NIOBIUM",
    "metal": "niobium",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["Nb", "COLUMBIUM"],
    "density_g_cm3": 8.57,
    "melting_point_c": 2477,
    "iso_reference": null,
    "wikidata_qid": "Q713",
    "notes": "Niobium. Hypoallergenic, anodizable to wide color range without coating. Common in alternative wedding bands.",
    "see_also": ["TI", "ZIRCONIUM"],
    "sources": []
  },
  {
    "stamp": "CHUK_KAM",
    "metal": "gold",
    "purity": 0.990,
    "fineness": 990,
    "region": ["HK", "CN"],
    "aliases": ["足金", "990 GOLD"],
    "color_variants": ["YG"],
    "iso_reference": null,
    "wikidata_qid": null,
    "notes": "Cantonese 'sufficient gold' designation, traditionally ≥99% pure gold. Standard for Hong Kong and Chinese bridal gold jewelry. Regulated under Hong Kong Trade Descriptions Ordinance.",
    "see_also": ["990", "999"],
    "sources": ["Hong Kong Trade Descriptions Ordinance Cap. 362"]
  },
  {
    "stamp": "1000 GOLD",
    "metal": "gold",
    "purity": 1.000,
    "fineness": 1000,
    "karat": 24,
    "region": ["HK", "CN"],
    "aliases": ["千足金", "999.9"],
    "color_variants": ["YG"],
    "iso_reference": "Hong Kong TDO",
    "wikidata_qid": "Q897",
    "notes": "Cantonese 'thousand-sufficient gold' designation, marketing 99.9%+ purity gold. Higher than chuk kam. Specific in Hong Kong/Mainland China gold trade.",
    "see_also": ["CHUK_KAM", "999"],
    "sources": ["Hong Kong Trade Descriptions Ordinance Cap. 362"]
  },
  {
    "stamp": "PINCHBECK",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["UK-historic"],
    "aliases": [],
    "alloy_components": ["copper", "zinc"],
    "iso_reference": null,
    "wikidata_qid": "Q852725",
    "notes": "Pinchbeck: 18th-century copper-zinc alloy designed to imitate gold. Named for inventor Christopher Pinchbeck. Costume/Georgian-era jewelry; collectible despite lacking precious-metal content.",
    "see_also": ["BRASS"],
    "sources": []
  },
  {
    "stamp": "TOMBAC",
    "metal": "base",
    "purity": null,
    "fineness": null,
    "region": ["EU-historic"],
    "aliases": ["TOMBAK"],
    "alloy_components": ["copper", "zinc"],
    "iso_reference": null,
    "wikidata_qid": "Q2511858",
    "notes": "Tombac: copper-zinc alloy with high copper content (~85%). Used in historical European jewelry imitating gold and in non-precious decorative work.",
    "see_also": ["PINCHBECK", "BRASS"],
    "sources": []
  },
  {
    "stamp": "MARCASITE",
    "metal": "decorative-mineral",
    "purity": null,
    "fineness": null,
    "region": ["international"],
    "aliases": ["IRON PYRITE"],
    "iso_reference": null,
    "wikidata_qid": "Q207935",
    "notes": "Marcasite: iron pyrite (FeS2) used as small faceted accent stones, particularly in Victorian and Art Deco silver jewelry. The 'marcasite' jewelry trade designation usually refers to pyrite, not true marcasite (which oxidizes).",
    "see_also": ["STERLING"],
    "sources": []
  },
  {
    "stamp": "JET",
    "metal": "organic",
    "purity": null,
    "fineness": null,
    "region": ["UK", "international"],
    "aliases": ["Whitby jet"],
    "density_g_cm3": 1.3,
    "iso_reference": null,
    "wikidata_qid": "Q199789",
    "notes": "Jet: fossilized wood (lignite), used in Victorian mourning jewelry. Whitby (UK) jet is the historical premium source. Lightweight, warm to touch (unlike glass), takes a high polish.",
    "see_also": [],
    "sources": []
  }
]