The British Hallmark: A UK Hallmarking Guide
For over 700 years, the British hallmark has been the UK's guarantee that precious metal jewellery is exactly what it claims to be. Under the Hallmarking Act 1973, any gold, silver, platinum or palladium piece sold in the UK above a legal weight must be independently tested and hallmarked by one of the four UK Assay Offices. That independent testing is what separates a verified piece of British jewellery from an unverified one.
What is a British hallmark?
A hallmark is a set of small official marks struck or laser-engraved into precious metal after it has been independently tested ("assayed"). It certifies three things: the purity of the metal, who made or submitted the piece, and which Assay Office tested it.
UK hallmarking began in 1300 under King Edward I, when testing was centred at Goldsmiths' Hall in the City of London - the origin of the word "hallmark" itself. The leopard's head, London's town mark, has been struck there ever since and remains one of the most trusted symbols in jewellery anywhere in the world.
The anatomy of a UK hallmark
A modern UK hallmark has three compulsory marks, plus two traditional marks that most offices still apply:
Sponsor's mark
The registered mark of the maker or company that submitted the piece - unique initials inside a shield, registered with an Assay Office and never re-issued.
Fineness mark
The millesimal purity number - parts of precious metal per thousand. 750 means 75% pure gold (18ct); 950 means 95% pure platinum.
Assay office mark
Shows which of the four UK Assay Offices tested the piece - London's leopard's head, Birmingham's anchor, Sheffield's rose or Edinburgh's castle.
Traditional symbol
The historic metal symbols: a crown for gold, the lion passant for sterling silver, Britannia for 958 silver and an orb for platinum.
Date letter
The year the piece was hallmarked. Voluntary since 1999 but still widely used - all four offices share the same letter, changing each January.
The four UK Assay Offices
Only four offices in the UK are authorised to test and hallmark precious metals:
London
The leopard's head. The Goldsmiths' Company Assay Office at Goldsmiths' Hall - where British hallmarking began over 700 years ago.
Birmingham
The anchor. Founded in 1773 to serve the Jewellery Quarter, today the largest Assay Office in the UK.
Sheffield
The rose. Also founded in 1773; the Yorkshire rose has been its mark ever since.
Edinburgh
The castle. Scotland's Assay Office, hallmarking since the 15th century.
When is a hallmark legally required?
The Hallmarking Act 1973 makes it illegal to sell or describe an item as gold, silver, platinum or palladium in the UK without a hallmark once it exceeds these exemption weights:
| Metal | Hallmark required above |
|---|---|
| Gold | 1.0 gram |
| Silver | 7.78 grams |
| Platinum | 0.5 grams |
| Palladium | 1.0 gram |
Fineness standards: what the numbers mean
The fineness number in a hallmark states purity in parts per thousand. These are the standards you will see on British jewellery:
| Metal | Hallmark number | Purity | Also known as |
|---|---|---|---|
| Gold | 375 | 37.5% gold | 9 carat |
| Gold | 585 | 58.5% gold | 14 carat |
| Gold | 750 | 75.0% gold | 18 carat |
| Gold | 916 | 91.6% gold | 22 carat |
| Silver | 925 | 92.5% silver | Sterling |
| Silver | 958 | 95.8% silver | Britannia |
| Platinum | 950 | 95.0% platinum | Platinum 950 |
| Palladium | 950 | 95.0% palladium | Palladium 950 |
Other recognised UK standards include 990 and 999 gold, 800 and 999 silver, 850, 900 and 999 platinum, and 500 and 999 palladium.
Why the hallmark matters when you buy
Verified purity. You cannot tell 18ct gold from 9ct by look or weight alone - the hallmark proves the metal is what the seller describes.
Legal protection. A hallmark means the piece passed independent testing under UK law, not just the seller's own claim.
Traceability. The sponsor's mark identifies exactly who made or submitted your piece, forever.
Lasting value. Hallmarked jewellery is easier to insure, resell and hand down, because its quality is independently documented.
British hallmark FAQs
Is a hallmark a legal requirement in the UK?
Yes. Under the Hallmarking Act 1973, any article described as gold, silver, platinum or palladium must carry a UK hallmark once it exceeds the exemption weight: 1 gram for gold, 7.78 grams for silver, 0.5 grams for platinum and 1 gram for palladium. Selling unhallmarked precious metal above these weights is a criminal offence.
What are the three compulsory marks in a UK hallmark?
The sponsor's mark (who made or submitted the piece), the millesimal fineness mark (metal purity in parts per thousand, such as 750 for 18ct gold) and the assay office mark (which of the four UK offices tested it). The traditional fineness symbol and date letter are voluntary additions.
Is the date letter still required on a hallmark?
No - the date letter has been a voluntary mark since 1999. Most pieces still carry one because it makes dating a piece easy. All four UK Assay Offices use the same letter, which changes every January.
What does the leopard's head mark mean?
The leopard's head is the town mark of London. It shows the piece was tested and hallmarked by the Goldsmiths' Company Assay Office at Goldsmiths' Hall, where British hallmarking began in 1300.
Does 18ct gold jewellery need a hallmark?
Yes, if it weighs more than 1 gram - which covers virtually all gold rings, bracelets, earrings and necklaces. An 18ct gold piece will show the number 750 in its hallmark, confirming it is 75% pure gold.
Where can I find the hallmark on my ring?
Look inside the band (the shank). Most modern rings are laser-hallmarked there with a small row of marks: the fineness number, the sponsor's mark and the assay office mark, often with a date letter. A jeweller's loupe makes them easy to read.
What is the difference between 9ct, 14ct and 18ct gold?
The carat states how much pure gold is in the alloy: 9ct is 37.5% pure (hallmarked 375), 14ct is 58.5% pure (585) and 18ct is 75% pure (750). Higher carat means richer colour and higher value; lower carat is harder-wearing.