Almost every piece of gold jewellery sold in Britain carries a row of very small marks, usually inside a ring shank or on a clasp. Most people never look at them, and the ones who do generally cannot read them. They are worth reading, because they are the only part of a piece of jewellery whose accuracy does not depend on trusting the person selling it.
A hallmark is struck by an assay office, which is independent of the maker and the shop and has no interest in the sale. It is a legal requirement under the Hallmarking Act 1973, and describing an article as gold without one is an offence rather than a matter of taste.
The three marks that must be there
Since 1999, a UK hallmark has three compulsory parts.
The sponsor’s mark. Two or more letters in a shaped surround, registered to whoever submitted the piece. It identifies who is responsible for the article, which is not always the same as who designed it.
The fineness mark. A three-digit number telling you how much gold is in the alloy, in parts per thousand. This is the one worth learning.
The assay office mark. A small symbol saying which office tested the piece.
A fourth mark, the date letter, has been optional since 1999. Many pieces still carry one, and it is the only part of a hallmark that tells you the year.
The number, which is the part that matters
Gold is never used pure in jewellery, because pure gold is too soft to hold a stone or survive a decade of wear. It is alloyed, and the fineness mark says how much of the alloy is gold.
| Mark | Carat | Gold content |
|---|---|---|
| 375 | 9ct | 37.5% |
| 585 | 14ct | 58.5% |
| 750 | 18ct | 75% |
| 916 | 22ct | 91.6% |
So a piece marked 375 is 9 carat, which is the answer to the question people most often arrive at this subject asking. It is gold, it is legally gold, and just over a third of it is gold.
Which office tested it
Four assay offices operate in the United Kingdom, and each has its own symbol.
- Birmingham: an anchor
- London: a leopard’s head
- Sheffield: a rose
- Edinburgh: a castle
Birmingham’s anchor is the oldest story of the four. By long-standing trade account it was settled over a pub table in 1773, when Birmingham and Sheffield were jointly pressing Parliament for their own assay offices and the Crown and Anchor tavern was where the campaign met: one city took the crown, the other the anchor. Sheffield struck that crown until 1975, when its mark became the rose it uses today. Birmingham has been striking the anchor without interruption ever since.
How to actually check one
Take the piece somewhere with good light and use magnification. A jeweller’s loupe is ideal, but the macro mode on a phone camera works well enough, and enlarging the photograph afterwards is easier than squinting.
Look inside a ring shank, along the edge of a pendant bail, or on the clasp of a chain. The marks are deliberately small and often worn, particularly on an older ring that has been resized or polished many times.
If you cannot find any marks at all, that is not proof of anything on its own. Gold articles under one gram are exempt from hallmarking, which covers a good deal of fine chain and many small earrings.
Is hallmarked gold “pure”?
No, and it is not meant to be. A hallmark is not a purity certificate. It is a statement of fineness: an independent confirmation that the alloy contains at least the proportion of gold that the number claims.
Which leads to the other common question, which is which fineness is best. There is no answer to that in the abstract. Higher gold content gives a warmer, deeper colour and costs more. Lower gold content gives a harder, more scratch-resistant metal. A 9ct band will survive a building site better than a 22ct one; a 22ct piece will look like nothing else in the room. Neither is a better metal, they are different decisions, and anyone who tells you one is simply superior is selling the one they have.
What it means when a piece is made for you
A hallmark can only be struck on a finished article, which is why it sits at the end of a commission rather than the beginning. The piece is cast, set and finished, then sent away to be tested by people who have never met you and do not care what it cost.
That is the point of it. Everything else about a piece of jewellery is the maker’s account of their own work. The hallmark is the one line written by somebody with nothing to gain.
