Gold Jewelry Stamp Decoder: What the Mark Inside Your Ring Means

Last updated: August 2026

What do the numbers on a gold stamp mean?

Two systems, one meaning. Karat counts parts of gold out of 24, so 18K is 18 parts gold and 6 parts alloy. Millesimal fineness counts parts out of 1,000, so the same metal is 750. Neither number is a grade: a 10K ring is not worse than an 18K ring, it is harder, paler and cheaper, because the alloy that dilutes the gold is what lets the metal survive a door frame. The gold purity guide covers how the ratio changes colour and hardness, and 14k vs 18k gold takes the two common options head to head.

What does each stamp actually mean?

The gold, silver, platinum and palladium finenesses below are those recognised under the international Hallmarking Convention; the plated and filled rows follow the United States jewellery guides at 16 CFR Part 23, which set the thresholds a mark has to meet before it may be used.

Why does my ring say K18 instead of 18K?

Because the karat letter is written in front in the Japanese convention rather than behind. K18 and 18K are the same 75% gold, and both correspond to a 750 stamp. K14 and K10 follow the same pattern. The answer is dull on purpose: the marking convention changes by country, the gold does not. What K18 does not tell you is where the piece was made, who made it, or whether the stone in it is what the seller said.

What do platinum, palladium and silver stamps mean?

Platinum-group marks work in parts per thousand, like millesimal gold. The recognised platinum finenesses are 850, 900, 950 and 999, and the U.S. guides treat the word “platinum” used without a number as a claim to the 950 standard. Where a second platinum-group metal is in the alloy, the mark is expected to put a number in front of each metal, as in 600Pt.350Ir.; run-together marks naming iridium and platinum without numbers tell you which metals are present and nothing about the proportions. On the silver side, “Sterling” or “Ster.” means at least 925 parts silver per thousand, which is why a bare 925 stamp means the same thing, and palladium is recognised at 500, 950 and 999. If you are weighing a white metal against white gold, platinum vs white gold covers what the difference does in wear.

Does GF, GP or HGE mean the piece is real gold?

It means there is real gold on the surface and base metal underneath. What matters is thickness and how the layer was attached. Gold filled is a gold layer bonded mechanically to a base, and it must account for at least one twentieth of the article by weight before the term may be used — hence the fraction in 1/20 12K GF. Rolled gold plate is the same bonded construction at one fortieth. Electroplate is deposited chemically and is thinner by orders of magnitude; heavy gold electroplate is the thicker version of it.

So the ranking runs: solid karat gold, gold filled, rolled gold plate, heavy electroplate, ordinary plate. Vermeil sits apart because the body underneath is sterling silver, so it keeps melt value after the gold wears through. A plated piece has almost no metal value.

What is the difference between a maker’s mark and an assay mark?

They answer different questions. An assay mark is applied by an independent office that tested the metal, and in a full United Kingdom hallmark it sits alongside a compulsory millesimal fineness number. That is third-party verification, which is the whole point of hallmarking.

A maker’s mark is not that. The London Assay Office is explicit that what people informally call a maker’s mark is a sponsor’s mark, whose purpose has always been to establish who is responsible for submitting the article rather than who manufactured it. Initials in a shield tell you which registered party stands behind the piece — useful, but not a purity test. The United States has no assay office system, so a karat number struck by the manufacturer is a self-declaration backed by law rather than an independent assay.

Does a missing stamp mean the piece is fake, and what can a stamp not tell you?

No, and this is where most decoder articles quietly overreach. A stamp can be absent because it wore off the inside of a band, because it was polished away during a resize, because the piece predates the marking convention in its country, or because it sits on a part that was later replaced. Equally, a stamp can be present and wrong: a mark is metal struck into metal, and nothing about the act of stamping proves the claim.

What no stamp can tell you: the weight of gold in the piece, the identity or quality of any stone set in it, whether the shank and the head are the same alloy, or what the piece is worth. Those are answered by weighing, testing and a grading report, not by reading. A laboratory jewellery report closes part of the gap — IGI’s jewellery reports describe the article and record precious metal content and purity stamps where present, alongside the graded stones. Beyond Carat works that way: every diamond is graded by IGI, the International Gemological Institute, and the report ships in the box. The honest limit is that it is IGI only, with no GIA option, so a buyer whose appraiser asked for a particular laboratory by name will need to look elsewhere. The IGI vs GIA comparison sets out what each settles.

Frequently asked questions

Is K18 the same as 18K gold?

Yes. K18 is the Japanese way of writing 18-karat gold — 75% gold by weight, the same standard as an 18K or 750 stamp anywhere else. The mark states purity only. It says nothing about where the piece was made or how good it is.

What does 585 mean stamped on a ring?

585 parts gold per 1,000, which is 58.3% gold, which is 14 karat. It is the millesimal way of writing the same purity as a 14K stamp, and it is the form used across most of Europe.

Is gold filled jewellery worth anything?

More than plated, far less than solid. A gold filled mark means the bonded gold layer is at least one twentieth of the article by weight, so there is recoverable gold in it, but the body is base metal and the resale value is closer to plated than to karat gold.