A UK hallmark is independent evidence of precious-metal fineness. For gold articles above the legal exemption weight, hallmarking is a key consumer-protection check when the item is described as gold.
The three compulsory parts
A complete UK hallmark contains a sponsor’s/maker’s mark, a metal and fineness mark, and an Assay Office mark. Optional marks can also appear.
London gold assay marks: what to look for
If you are trying to identify a London gold assay mark, start with the leopard’s head. That is the current Assay Office town mark for London. It should be read alongside the sponsor’s mark and the millesimal fineness mark rather than treated as proof on its own.
For gold, common fineness numbers include 375 (9ct), 585 (14ct), 750 (18ct) and 916 (22ct). A date letter may also appear, but it is optional in the modern UK hallmark.
Leopard’s head = London Assay Office. Then check the sponsor’s mark and the gold fineness number. On older jewellery, mark styles can vary by period, so use an official hallmark reference before assigning a date.
Common gold fineness numbers
| Mark | Equivalent | Minimum gold content |
|---|---|---|
| 375 | 9ct | 37.5% |
| 585 | 14ct | 58.5% |
| 750 | 18ct | 75% |
| 916 | 22ct | 91.6% |
The 1 gram gold exemption
Gold articles weighing less than 1 gram are exempt from compulsory hallmarking in the UK. For articles consisting of precious and base metal, official guidance notes that the exemption weight is based on total metal weight. The exemption does not mean every unhallmarked gold-coloured item is genuine.
- Match the seller’s metal description to the hallmark information.
- Ask for sharp photographs of all marks on higher-value pieces.
- Check stated gram weight as well as length and width.
- Do not treat a lone 375, 585 or 750 stamp as equivalent to a complete UK hallmark.
Why a single stamp is not the same as a full hallmark
A number such as “750” can be useful information, but a complete UK hallmark includes the compulsory marks above. When buying online, ask for clear photographs of the hallmark and compare the description with the item.
Gold-plated silver is different
Gold-plated silver is hallmarked as silver where hallmarking applies. UK guidance restricts potentially confusing standalone gold-fineness markings on gold-plated silver. Always read the full material description.
Editorial note: hallmarking rules can change. For legal requirements, consult the British Hallmarking Council/GOV.UK guidance rather than relying solely on this guide.