Education
The Stamps Inside Your Ring, Decoded
585, 750, PT950, S925 β and the ones that mean the piece is not solid at all.
Written by the Mapple Gems workshop, Surat Β· Updated 14 September 2026
Short answer
A fineness stamp states purity in parts per thousand: 375 = 9K, 585 = 14K, 750 = 18K, 925 = sterling silver, PT950 = platinum. A number alone means solid metal. A number with letters after it β GP, GF, HGE, RGP, or β925β on a gold-coloured ring β means plated or filled over a base. And a makerβs fineness stamp is not the same as an official hallmark, which is applied by a state assay office.
Every solid piece of jewellery carries a small stamp inside, and it is the single most checkable fact about the object. It takes a loupe or a phone camera and thirty seconds, and it settles a question no product description can.
Solid metal stamps
| Stamp | Means | Also written as |
|---|---|---|
| 375 | 37.5% gold | 9K, 9ct |
| 417 | 41.7% gold | 10K |
| 585 | 58.3% gold | 14K, 14ct |
| 750 | 75% gold | 18K, 18ct |
| 916 | 91.6% gold | 22K |
| 925 | 92.5% silver | Sterling, S925 |
| PT950 / 950 | 95% platinum | Plat, PLAT |
| PD950 | 95% palladium | Pall |
Note that these are the same information written two ways. 585 and 14K are identical; a piece may carry either.
The letters after a number are what tell you it is not solid. This is the decoder that matters most, and it is entirely legal and disclosed β simply read past by people scanning for a familiar number. GP = gold plated. GF or 1/20 14K GF = gold filled, a thicker layer but still a layer. HGE = heavy gold electroplate. RGP = rolled gold plate. GEP = gold electroplate. And the one that catches most people: a β925β stamp on a gold-coloured ring means sterling silver with a gold plating over it β vermeil. In every one of these the base metal is what sits against your skin once the layer wears through, which for a ring is the back of the shank within a couple of years. A number with no letters after it means solid. That is the whole rule.
Fineness stamp vs official hallmark
These are often confused and they are different things.
A fineness stamp β 585, 750, 925 β is applied by the maker and states what the metal is. It is a regulated description in most markets, so misstating it is a legal matter rather than a matter of opinion, but it is not independently verified.
An official hallmark is applied by a state or federal assay office after testing, and typically comprises several marks together: a sponsor or makerβs mark, a fineness mark, an assay office mark, and sometimes a date letter. It is mandatory in the UK, France, the Netherlands, Ireland and under Switzerlandβs control regime, and not required in many other markets including Germany, Canada, Australia and the United States.
So an unhallmarked ring is not suspicious β most of the world does not require it. An unstamped ring is a different matter, and worth asking about.
Other marks you may see
- A makerβs mark β initials or a symbol identifying who made it.
- A country mark on imported pieces in some markets.
- A size number, occasionally, though most workshops omit it.
- βLGβ or βLGDβ on a girdle inscription, indicating a laboratory-grown stone.
- A report number laser-inscribed on the girdle β the only thing tying a grading report to your particular stone.
How to read them
- Look inside the shank, usually near the bottom or beside the join.
- Use a phone camera on macro with good light β easier than a loupe for most people.
- Photograph it and zoom in rather than squinting; stamps are frequently under a millimetre.
- Note everything you see, including makerβs marks β the combination tells more than any single mark.
If there is no stamp, or it is worn away
Common on older rings, since a stamp sits inside the shank where wear is heaviest, and it can be polished away over decades or removed during a resize.
The answer is testing rather than guessing. A jeweller can run an acid test or an XRF reading and give you the fineness in minutes, for very little. Do this before ordering a matching band or having any work done β assuming 585 when a ring is 750 produces a visible shade mismatch that cannot be fixed afterwards.
Why it matters practically
Three situations where the stamp is the deciding fact. Matching a wedding band β 14K yellow beside 18K yellow is visibly different, so βyellow goldβ is not a specification and 585 or 750 is. Repair and resizing β a jeweller needs the fineness to use matching solder. And verifying a purchase β a ring sold as 14K that tests as 10K is not a warranty question but a not-as-described one, where your rights are strongest.
Keep reading
Frequently asked questions
What does 585 mean inside a ring?
58.3% gold, which is the same as 14K β the two are identical information written different ways. Other common fineness stamps are 375 for 9K, 417 for 10K, 750 for 18K, 916 for 22K, 925 for sterling silver and PT950 for platinum.
How can I tell if a ring is plated from the stamp?
Letters after the number. GP is gold plated, GF or 1/20 14K GF is gold filled, HGE is heavy gold electroplate, RGP is rolled gold plate, and a 925 stamp on a gold-coloured ring means silver with gold plating β vermeil. A number with no letters after it means solid.
Is a fineness stamp the same as a hallmark?
No. A fineness stamp is applied by the maker and states what the metal is; an official hallmark is applied by a state assay office after testing and usually comprises several marks together. Hallmarking is mandatory in the UK, France, the Netherlands, Ireland and Switzerland, and not required in many other markets β so an unhallmarked ring is not suspicious.
What if the stamp inside my ring has worn away?
Have it tested rather than guessing β an acid test or XRF reading gives the fineness in minutes for very little. Do it before ordering a matching band or having work done, since assuming 585 when a ring is 750 produces a visible shade mismatch that cannot be corrected afterwards.
A number with no letters after it means solid.
Everything we make carries one β 925, 417, 585 or 750, and nothing plated.
Leave a comment