What is a hallmark?
In the UK, a hallmark is a set of marks applied by an independent assay office after testing confirms the precious-metal content of an item. Hallmarking is governed by the Hallmarking Act 1973.
The three compulsory marks
- Sponsor's mark — usually initials in a shield, identifying the maker or the business that submitted the item.
- Fineness mark — a number showing the precious-metal content in parts per thousand.
- Assay office mark — showing where the item was tested: London (leopard's head), Birmingham (anchor), Sheffield (rose) or Edinburgh (castle).
Optional marks can include a date letter, a traditional fineness symbol (a crown for gold) and the Common Control Mark used under an international convention.
Common gold fineness numbers
| Mark | Carat | Gold content |
|---|---|---|
| 375 | 9 carat | 37.5% gold |
| 585 | 14 carat | 58.5% gold |
| 750 | 18 carat | 75.0% gold |
| 916 | 22 carat | 91.6% gold |
| 990 | — | 99.0% gold |
| 999 | 24 carat | 99.9% gold |
Not every gold item is hallmarked
UK rules include exemptions — for example, gold items below a minimum weight (currently 1 gram) do not need a hallmark. Older pieces and items made abroad may carry different marks or none at all. A missing hallmark does not mean an item is not gold.
Marks that can mislead
Some stamps describe a surface layer rather than solid gold, such as "GP" (gold plated), "RGP" (rolled gold plate) or "GF" (gold filled). Marks can also be worn, partial or, occasionally, not genuine.
Why assessment still matters
Hallmarks are a useful guide, but what can be bought is determined by assessment of the item itself. Find out more in how gold is assessed, or read our guide to selling gold by post safely.