Jewelry Hallmarks Guide: What Every Stamp on Gold & Silver Means (2026)

For a direct comparison of the two most popular karats, read our 14K vs 18K gold guide — covering durability, color, price, and which is better for daily wear.

What Do Jewelry Hallmarks Mean?

You're looking at a piece of jewelry and notice a tiny stamped number or abbreviation. What does it mean? Is this real gold? Is it sterling silver? Is it plated? Those tiny marks — called hallmarks — tell you everything you need to know about what the metal actually is. This guide covers every hallmark you'll encounter on gold, silver, and plated jewelry, with a complete reference table for each metal type.

What Are Jewelry Hallmarks?

A jewelry hallmark is an official stamp applied to precious metal items to certify their metal content. The practice dates to 14th-century England, when goldsmiths in London were required to bring their work to Goldsmiths' Hall for assay and marking — hence "hallmark." Today, hallmarking systems vary by country but serve the same purpose: protecting buyers from misrepresented metal quality.

According to the Jewelers of America, the US Federal Trade Commission requires jewelry sold as gold to be accurately described by karat, and pieces stamped with a karat quality mark must be within a half-karat of the stated quality.

Two hallmarking systems exist side by side globally:

• Karat system (US, UK, Middle East): expresses gold purity as parts out of 24 — 18K = 18/24, 14K = 14/24
• Millesimal fineness (Europe): expresses purity as parts per 1,000 — 750 = 750/1,000 = 75%, 585 = 58.5%

Both systems coexist on the same SERPs because jewelry moves across markets. A European piece says 750 where an American piece says 18K — same gold, different notation.

Gold Hallmarks — Complete Reference Table

Every gold hallmark corresponds to a specific karat and purity percentage. This table covers all gold hallmarks you're likely to encounter:

Key rule: In the US, any piece must be at least 10K (41.7% gold) to be sold as gold jewelry. In the UK and Australia, 9K (37.5%) is the legal minimum. A piece stamped 375 is legal fine gold in London but technically can't be called gold jewelry in New York.

Silver Hallmarks — Complete Reference

Shopping or selling in the UK specifically? Purity stamps like 925 are only half the picture — UK law also has its own legal hallmarking weight thresholds. See our UK Hallmarking Law Guide for the full legal requirements, the four UK Assay Offices, and why lightweight silver jewellery is often exempt.

Silver jewelry uses a different scale — fineness expressed as parts per 1,000 (the millesimal fineness system):

Gold Plated, Filled & Electroplate Marks

These marks tell you the piece is NOT solid gold — it has a gold coating over a base metal:

A related term: gold vermeil is a US government standard for gold-plated jewelry that requires a 925 sterling silver base and a minimum 2.5-micron gold layer. Pieces stamped "925" with a gold finish often qualify as vermeil, though the stamp itself just confirms the silver base — not the gold thickness.

A stamp like 18K GP means the gold layer is 18K purity, but the piece is plated — not solid 18K gold. The 18K refers only to the quality of the plating layer.

How to Read a Jewelry Hallmark

Follow these four steps:

1. Find the stamp. Look inside the ring band, near the clasp on necklaces and bracelets, or on the post of earrings. You may need a jeweler's loupe (10× magnification) for small pieces.
2. Identify the mark type. Is it a number (925, 750, 585)? A karat stamp (18K, 14K)? An abbreviation (GP, HGE, GF)? Or a maker's mark (initials in a shield or oval)?
3. Cross-reference the table. Numbers = fineness (use the tables above). Karat stamps = direct purity. Abbreviations = plated/filled.
4. Check for additional marks. Many pieces carry multiple stamps — a fineness mark AND a maker's mark AND a country of origin. The fineness mark is what tells you metal quality.

If you can't find any stamp at all on a piece sold as gold or silver, that's a concern. In the US and UK, sellers are legally required to accurately represent metal content. A legitimate jeweler will always provide documentation or testing if asked.

How to Tell If Jewelry Is Real Gold

Use this decision tree:

• ✅ Stamped 10K, 14K, 18K, 22K, 24K (or their European equivalents 417, 585, 750, 916, 999) → Real solid gold
• ✅ Stamped 18K GP or 18K GF → Gold plated/filled — real gold coating, not solid gold
• ⚠️ Stamped HGE, GEP, GP alone → Plated — gold surface layer only
• ⚠️ No stamp at all → Unverified — request documentation or professional acid test
• ❌ Turns skin green → Copper-heavy base metal, very thin or no plating

If in doubt, take the piece to a local jeweler for an acid test. Most will test while you wait at minimal cost.

Hallmark Systems by Country

For a full comparison of 10K and 14K gold, see our 10K vs 14K gold guide.

Plating & Abbreviation Stamps: 18KGP, GP, STG

Beyond karat and fineness numbers, jewelry is often stamped with plating and material abbreviations. Here's what the most common ones mean:

• 18KGP (also written 18K GP) — 18-karat gold plating (75% pure gold) applied by electroplating over a base metal. "18K" confirms the gold purity used for plating; "GP" confirms it's plated, not solid. When paired with "925," the base is sterling silver — the best possible base for gold plating, and hypoallergenic. Full guide: what does 18KGP mean.
• GP alone — Gold Plated, karat purity unspecified. Ask the brand what karat gold was used for the plating. Full guide: what does GP mean.
• STG or Sterling — shorthand for 925 sterling silver (92.5% pure). Functionally identical to a "925" stamp.
• "18K 925" or "925 18K" — the strongest gold-plated combination: 18K gold plating confirmed over a 925 sterling silver base, both hypoallergenic.

Frequently Asked Questions

What are jewelry hallmarks?

Jewelry hallmarks are small stamped marks that certify a metal's purity. Gold marks include karat numbers (10K, 14K, 18K) or European fineness numbers (417, 585, 750). Silver uses 925 for sterling. Plated pieces show GP, HGE, or GF.

What does 925 mean on jewelry?

925 means 92.5% pure silver — sterling silver. It's the global standard for silver jewelry. The remaining 7.5% is usually copper for hardness. See our full guide: what does 925 mean.

What does 750 mean on jewelry?

750 means 75% pure gold — the European millesimal fineness mark for 18K gold. A piece stamped 750 is identical in purity to one stamped 18K. Full guide: what does 750 mean.

What does 585 mean on jewelry?

585 means 58.5% pure gold — the European mark for 14K gold. Identical to 14K. Full guide: what does 585 mean.

What does 417 mean on jewelry?

417 means 41.7% pure gold — the European mark for 10K gold. The minimum karat legally sold as gold in the US. Full guide: what does 417 mean.

What does 375 mean on jewelry?

375 means 37.5% pure gold — the hallmark for 9K gold, used mainly in the UK, Ireland, and Australia. Not legal as gold in the US. Full guide: what does 375 mean.

What does HGE mean on jewelry?

HGE = Heavy Gold Electroplate. The piece has a thick electroplated gold coating over a base metal — it's not solid gold. Full guide: what does HGE mean.

What does 18KGP mean on jewelry?

18KGP means 18-karat gold plating — an 18K gold layer electroplated over a base metal, most often 925 sterling silver. It's not solid gold, but on a sterling silver base it's hypoallergenic and visually identical to solid 18K. Full guide: what does 18KGP mean.

What does STG mean on jewelry?

STG is shorthand for Sterling — the same as a 925 stamp, meaning 92.5% pure silver. See our what does 925 mean guide for the full breakdown.

How do I know if jewelry is real gold?

Look for a karat stamp (10K, 14K, 18K) or European fineness (417, 585, 750) inside the band or near the clasp. GP, GF, or HGE stamps mean plated/filled — not solid gold. No stamp at all = request documentation or a professional acid test.

What does 925 Italy mean on jewelry?

925 Italy means 92.5% pure sterling silver, made in Italy. Same purity as any 925 stamp — the "Italy" indicates country of manufacture. Full guide: what does 925 Italy mean.

What is the difference between 14K and 18K gold jewelry?

14K = 58.3% gold (European mark: 585). 18K = 75% gold (European mark: 750). 18K has richer color and is more hypoallergenic. Hallmarks also help you identify which metals are safe for sensitive skin — see our jewelry for sensitive skin guide for the full safe vs. problematic metals breakdown. 14K is harder and better for daily-wear rings. Most US engagement rings are 14K. Most luxury fine jewelry is 18K.

Your Complete Hallmark Reference

Every piece of fine jewelry carries a story in those tiny stamps. 750 tells you it's 18K gold made to European standards. 925 Italy tells you it's sterling silver from one of the world's finest jewelry-making traditions. GP tells you there's a gold layer — but underneath is something less precious. Understanding these marks makes you a more confident buyer and helps you care for your jewelry the right way.

Browse our full collection of 18K gold plated 925 sterling silver jewelry →

Written by Vaishakhi Ajmera, founder of AJLuxe — specialists in 18K gold plated sterling silver jewelry. Last updated: June 2026.

Once you know your hallmarks, learn how to tell if jewelry is real gold using the magnet test, skin test, and professional XRF testing. And keep your pieces looking new with our guide on how to clean silver jewelry.

Related: Sterling Silver vs Gold Plated Necklace Guide

Explore more: Complete Gold Jewelry Guide

Now that you understand jewelry hallmarks, see how they apply to popular brands: our Ana Luisa alternatives guide and Mejuri alternatives guide both cover material quality and base metal specs for 14–17 brands each.

No Hallmark? How to Test Metal at Home (and When Not To)

Stamps wear off vintage pieces, get filed down by resellers, or were never applied to begin with — so knowing how to verify metal without a hallmark matters as much as decoding one. Here's what actually works, and what damages jewelry instead of testing it.

• Magnet test (safe, quick): Real gold and sterling silver are not magnetic. If a piece clings to a strong magnet, the visible metal is a base-metal alloy, not solid gold or silver — though this won't catch thin plating over a non-magnetic base like brass or stainless steel.
• Water test (unreliable for plating): Solid gold sinks and doesn't tarnish, which is often cited as a home test. It only tells you something about solid metal all the way through — it can't distinguish 18K-plated sterling silver from solid gold, since both behave the same in water.
• Nitric acid test (skip this one): Jewelers use graduated acid drops on a touchstone to read karat by reaction. Don't try this at home on anything you want to keep — it's destructive on contact, and on plated jewelry it will eat straight through the gold layer to the base metal in seconds, leaving a permanent mark.
• Professional XRF testing: Most local jewelers and pawn shops have an X-ray fluorescence gun that reads exact metal composition in seconds with zero damage to the piece. This is the only reliable way to confirm karat or purity on a piece with no stamp, and it's usually free or under $10.

The practical takeaway: any test that scratches, files, or applies acid to the surface permanently damages gold-plated jewelry, because it's removing the thin gold layer itself, not just testing it. For plated pieces specifically, your best verification is the hallmark itself (18KGP, GP, HGE) plus a receipt or product listing that discloses base metal and plating thickness — not a DIY test that can ruin the piece you're trying to authenticate.

All third-party trademarks, brand names and product names are the property of their respective owners. AJLuxe is not affiliated with, endorsed by, sponsored by, or otherwise connected to any third-party brand referenced in this article. Brand names are used solely for accurate comparative reference, and material descriptions reflect each brand's own published product specifications at the time of writing.