Where to look
On a ring, inside the shank, opposite the setting. On a chain or bracelet, on the tongue of the clasp or on a small flat tag soldered beside it. On a pendant, on the back of the bail. On earrings, on the post or the butterfly back, which is why one earring of a pair is often marked and the other is not. On a watch case, on the back or inside the lugs.
Marks are small and frequently worn. A loupe or a phone camera at maximum zoom will read most of them. Clean the area with a dry cloth first, since decades of polish residue sit in the recess of a stamp and fill it in.
Gold
| Karat | Stamp | Gold by weight |
|---|---|---|
| 24k | 999 | 99.9% |
| 22k | 916 | 91.7% |
| 21k | 875 | 87.5% |
| 20k | 833 | 83.3% |
| 18k | 750 | 75.0% |
| 14k | 585 | 58.3% |
| 12k | 500 | 50.0% |
| 10k | 417 | 41.7% |
| 9k | 375 | 37.5% |
| 8k | 333 | 33.3% |
Ten karat is the legal floor for calling something gold in the United States. Britain allows 9k, stamped 375, which is why so much British estate jewellery carries a mark Americans do not recognise. Anything below the local floor has to be described as a gold alloy rather than gold.
Colour tells you about the alloy, not the purity. Yellow, white and rose gold at the same karat contain identical amounts of gold: the difference is copper for rose, palladium or nickel for white. White gold is usually rhodium plated on top, which adds nothing at melt and wears through in a few years, which is what people are seeing when a white gold ring turns yellowish.
Silver and platinum
| Standard | Stamp | Pure metal by weight |
|---|---|---|
| fine silver silver | 999 | 99.9% |
| Britannia silver | 958 | 95.8% |
| sterling silver | 925 | 92.5% |
| coin silver silver | 900 | 90.0% |
| European silver | 800 | 80.0% |
| 40% clad silver | 400 | 40.0% |
| pure platinum | 999 | 99.9% |
| Plat 950 platinum | 950 | 95.0% |
| Plat 900 platinum | 900 | 90.0% |
| Plat 850 platinum | 850 | 85.0% |
Platinum is also marked PLAT, PT950 or 950 PT. Palladium appears as PD950 or PALL. Both are denser than gold, so a platinum ring feels heavier than it looks, and both are worth checking the spot price for separately since they do not track gold closely.
Marks that are not purity marks
| Mark | Means | Note |
|---|---|---|
| GF | Gold filled | A bonded layer at a stated fraction of the weight, e.g. 1/20 12k GF. |
| RGP | Rolled gold plate | The same idea, thinner. Commonly 1/40. |
| GP | Gold plated | Electroplated, microns thick, no stated content. |
| HGE | Heavy gold electroplate | Still electroplate. The word heavy is marketing. |
| GEP | Gold electroplate | As above. |
| EPNS | Electroplated nickel silver | No silver at all. Nickel silver is a copper alloy. |
| German silver | No silver | A copper, nickel and zinc alloy named for its colour. |
The important reading skill here is that a karat number next to one of these marks describes the coating, not the piece. "1/20 12k GF" is not 12 karat gold. It is a twentieth of the weight in 12 karat gold, bonded to brass, and it prices completely differently.
Maker marks and assay marks
Alongside the fineness you will often find other punches. A maker or sponsor mark, usually initials in a shaped surround. A town mark, identifying the assay office: a leopard head for London, an anchor for Birmingham, a rose for Sheffield. And a date letter, a single character in a particular typeface and shield, which pins a British piece to a single year.
These are worth reading before anything goes to a refiner. A full British hallmark identifies the maker and the year, and a recognised maker can multiply the value of a piece well past its metal. The same goes for American marks such as Tiffany, Georg Jensen or a documented Navajo silversmith stamp.
When the mark is wrong
Counterfeit stamps exist, most commonly 925 on plated base metal and 14K or 18K on thinly plated chain. Three cheap checks: a magnet, since gold and silver are not magnetic and the steel cores of many fakes are. Weight against size, since brass and steel are much lighter than gold for the same bulk. And an acid test kit, which costs little and is definitive enough for a first pass. For anything valuable, an XRF reading at a jeweller settles the question without marking the piece.
Hallmark questions
What does 585 mean on gold?
It is 14 karat: 585 parts per thousand gold. The European standard alloys slightly richer than the American 14/24 figure of 583, and both are sold as 14k. If you see 583 or 585 on a ring, it is the same claim.
What does 750 mean on jewellery?
Eighteen karat gold, 750 parts per thousand, 75% gold by weight. It is the most common fine gold standard in Europe and the usual mark on Italian and French pieces.
What does 916 mean?
Twenty two karat gold, 91.6% pure. It is the standard for Indian, Gulf and much of South Asian jewellery, where gold is bought partly as savings and higher purity matters more than hardness.
Does 925 always mean sterling silver?
It is a claim of sterling, and on pieces from regulated markets it is reliable. It is also the single most counterfeited mark in jewellery, and appears on plated base metal from unregulated sources. Weight, a magnet and an acid test settle it quickly.
What if my jewellery has no stamp at all?
It may still be gold. Stamping has not always been universal, marks wear off thin bands over decades, and resizing can remove the stamped section entirely. Any jeweller will acid or XRF test an unmarked piece in seconds, usually for nothing.
What are British hallmarks?
A British hallmark is a set of separate punches: a sponsor mark for the maker, a fineness number, an assay office town mark and often a date letter. It is a legal assay rather than a manufacturer claim, which makes it the most trustworthy marking system in common circulation.
Does a karat mark guarantee purity?
In regulated markets it is a legal claim with tolerances, and it is generally accurate. It is not a test. Buyers assay anyway, because the cost of being wrong about a large lot is far greater than the cost of testing it.