Gold Purity Stamps & Karat Hallmarks Identification Guide
💡 Key Takeaways (Quick Reference)
- 585 Stamp = 14 Karat gold (58.5% pure gold), standard in American fine jewelry.
- 750 Stamp = 18 Karat gold (75.0% pure gold), standard in European luxury pieces & Art Deco engagement rings.
- 375 Stamp = 9 Karat gold (37.5% pure gold), widely used in British Victorian and Edwardian antique cameo mountings.
Understanding gold hallmarks and purity stamps is essential for evaluating antique, vintage, and modern fine jewelry. Hallmarks serve as an official guarantee of precious metal content and often reveal the origin, maker, and era of a piece.
Deciphering Karat vs. Millesimal Fineness Marks
Gold purity is designated by either Karatage (K or Kt)—used predominantly in the United States—or Millesimal Fineness (parts per thousand), which is the standard across Europe, Asia, and international markets.
| Karat Marking | Millesimal Fineness Stamp | Pure Gold Content | Common Application |
|---|---|---|---|
| 24K | 999 or 999.9 | 99.9% Pure | Investment bars, traditional Asian jewelry |
| 22K | 916 | 91.6% Pure | High-karat Indian and Middle Eastern gold |
| 18K | 750 | 75.0% Pure | Luxury engagement rings, European fine jewelry |
| 14K | 585 | 58.5% Pure | Most popular American fine jewelry standard |
| 10K | 417 | 41.7% Pure | Minimum US legal standard for solid gold |
| 9K | 375 | 37.5% Pure | Common British and Commonwealth antique gold |
Key Types of Gold Stamps & Abbreviations
When inspecting a ring band, necklace clasp, or brooch pin, you may encounter extra letters alongside the numeric mark:
- GF (Gold Filled): A thick layer of gold mechanically bonded to a base metal core. Must be at least 1/20th of the item’s total weight by law.
- GP / GEP (Gold Plated / Gold Electroplated): A thin layer of gold applied via electroplating over base metal.
- HGE (Heavy Gold Electroplate): Indicates a slightly thicker plating layer than standard GP.
- Rolled Gold / RGP: Similar to gold-filled, but with a thinner gold layer (often 1/30th or 1/40th weight).
- Vermeil: Sterling silver (925) plated with a heavy layer of gold (at least 2.5 microns thick).
How to Locate Hidden Stamps on Jewelry
- Rings: Inspect the inner surface of the shank/band under a 10x jeweler’s loupe. For vintage Art Deco rings, check near the lower gallery area.
- Necklaces & Bracelets: Check the end tabs, lobster claw clasps, spring rings, or small hang tags attached near the clasp.
- Earrings: Look on the post, earring back/clutch, or along the lower rim of hoops.
- Brooches & Cameos: Examine the reverse side, pin stem, or rim of antique cameo bezels.
What to Do If There Are No Hallmarks
Not all authentic gold jewelry bears a stamp. Items produced prior to national hallmarking legislation, custom hand-forged pieces, or resized rings where the mark was polished out may lack stamps.
Expert Advice: If your piece is un-stamped, perform a non-destructive touchstone acid test or an XRF (X-ray Fluorescence) scan at a certified jeweler to verify exact gold content.
Frequently Asked Questions
What does 585 mean on gold jewelry?
585 signifies 14 Karat gold, representing 58.5% pure gold alloyed with other metals for durability.
What does 750 stand for on a ring or necklace?
750 indicates 18 Karat gold, containing 75.0% pure gold. It is common in high-end European and luxury jewelry.
How can I tell if a gold mark is real or plated?
Look for stamps like GP (Gold Plated), GF (Gold Filled), or HGE (Heavy Gold Electroplate). Genuine solid gold typically uses karat numbers (10K, 14K, 18K) or millesimal fineness numbers (417, 585, 750, 916).
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