Gold hallmarks: what 375, 585, 750 and 916 mean on your jewellery

01

What the number in a gold hallmark says

Carats count in twenty-fourths and hallmarks count in thousandths. Pure gold is 24 carat, so 9 carat is nine parts in twenty-four, and nine divided by twenty-four is 0.375: that is where the 375 on a 9ct ring comes from. Every figure in the table below is the same sum done for a different carat, with the result rounded to the standard the assay offices test to.

UK gold standards: the hallmark figure and the carat it corresponds to

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Two of the figures look slightly off, and both are deliberate. Fourteen twenty-fourths is 583.3, but the UK standard is 585, set a little above the arithmetic. Twenty-two twenty-fourths is 916.67, and the legal standard behind the 916 mark is 916.6. In both cases a hallmark is a floor: it certifies that the gold content is at least the figure shown, and a piece may test slightly above it.

The colour of the gold tells you nothing about the number. White gold, yellow gold and rose gold of the same carat carry the same hallmark, because the difference is in the other metals in the alloy: more copper for rose, palladium or nickel for white. A white 18ct ring is 750 like a yellow one, and most white gold is also rhodium-plated, which is why an old white ring can look faintly yellow where the plating has worn through.

02

A UK gold hallmark, a foreign stamp, and the difference

The number alone is not the hallmark. A full UK hallmark on gold has three compulsory parts, usually struck in a short row: the sponsor's mark (initials in a shaped shield), the fineness figure in its surround, and the mark of the assay office that tested it. Optional marks, a crown and sometimes a date letter, may stand beside them. The row is the proof; any one part of it on its own is not.

• A crown beside the number is the traditional symbol for gold. It is optional, and its presence confirms what the number already says rather than adding to it.
• A leopard's head is London, an anchor is Birmingham, a rose is Sheffield and a three-towered castle is Edinburgh. If one of these is there, a UK assay office tested the piece.
• A pair of scales, with the fineness figure inside it or struck beside it, is the Common Control Mark of the Hallmarking Convention, struck by an assay office in a member country. The UK recognises it, so the piece has been independently tested even though the marks look foreign.
• A number with none of the above, whether 375, 585, 750, 9K, 14K or 18K, is the manufacturer's own claim. It may well be accurate, but nobody independent has tested it, so it is checked before anybody relies on it.

Order is less fixed than people expect. Birmingham Assay Office describes the usual modern sequence as sponsor's mark, then fineness, then office, but on a narrow ring shank or a chain tag the marks may be split, stacked or struck in a different order. What matters is that all three are present, not which comes first. The glossary has a short entry for each kind of mark if a term here is new to you.

The surround is part of the mark and not decoration. Silver's fineness sits in an oval, platinum's in a shape like a little house, and palladium's in three joined ovals (a trapezium on pieces marked in 2009), while gold's has its corners cut off. On a worn piece where the figure itself is hard to read, the outline that is left can still tell you which metal the assay office found.

03

Older gold: carat figures, 12ct and 15ct, and what they date

Gold hallmarked before the modern system does not always show a three-figure number. Older 18ct and 22ct pieces commonly carry the carat itself, 18 or 22, beside a crown. The lower standards arrived later: the Goldsmiths' Company Assay Office records that 9, 12 and 15 carat gold were introduced in 1854, marked with figures stating their fineness, and that in 1932 the 12 and 15 carat standards were withdrawn and 14 carat took their place.

That gives a seller a free dating clue. A British 15ct or 12ct hallmark puts the piece between 1854 and 1932, which is Victorian, Edwardian or early twentieth-century work: exactly the period where a brooch, a locket or a gem-set ring can be worth more to a collector than its gold. A 14ct British hallmark, by the same logic, is 1932 or later.

Gold standards that tell you roughly when a British piece was marked

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The last row is a tendency rather than a rule, because plenty of makers still ask for the crown and the date letter. The date letters guide explains how to read the letter itself, and why it gives the year of hallmarking rather than the year the piece was made.

04

Marks that mean plated, rolled or filled, not solid gold

An easy mistake with gold marks is reading a carat figure inside a plating mark as a hallmark. The figure describes the thin layer of gold on the outside, and the letters beside it say that is all there is. None of these is an assay office mark, and none of them was put there by anyone who tested the piece.

Stamps that look like gold marks but describe a coating

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18KGP is easy to misread, because the first three characters look exactly like an 18ct stamp and the last two are easy to miss under a worn surface. Read the whole stamp, not the first half of it. If it includes GP, GEP, HGE, HGP, RG, RGP or GF, before or after the carat, you are looking at a coating. A single extra letter on its own is not a reliable sign either way, so photograph the whole stamp and ask. The guide to plated, rolled and filled gold explains how each of these is made and why none of them is gold through.

05

Where the marks hide on rings, chains, earrings and watches

1. RingsInside the shank, usually at the back opposite the stone or the widest part. Resized rings sometimes lose part of the row where a piece was cut out or added.
2. Chains and braceletsOn a small flat tag beside the clasp, on the clasp itself, or on the end rings. A mark on the clasp alone tells you about the clasp; the chain is checked separately.
3. Pendants and locketsOn the bail, the loop the chain passes through, or on the back or inside edge of a locket.
4. Earrings and small charmsOften nothing at all. Gold articles under 1 g are exempt from hallmarking, so a pair of plain studs with no mark is normal.
5. WatchesInside the case back, not on the dial. A gold case can hold a steel movement, and a gold-filled case is often stamped to look like a solid one; the gold watches page covers what to look for.

A phone camera held close in daylight reads most of these better than the eye does. Rest the piece on something pale and plain, let the light fall across the mark rather than straight onto it so the edges throw a shadow, and take two or three pictures at slightly different angles. A photograph that a person can zoom into is worth more than a written description of what the mark looks like.

06

Seller risks and exceptions with gold marks

• 22ct gold stamped 916 abroad sometimes tests lower than the stamp. A UK hallmark is a tested minimum; a foreign 916 stamp is not, and the tested figure is the one that counts.
• A worn or partly polished-out hallmark still counts where enough of it can be read, but the less of it that survives, the more the identification rests on testing.
• A hallmark on a replaced clasp, or on a marked fragment soldered into an unmarked piece, describes only that part. Checks are made on the body of the item where a check can be made, not only where the mark is.
• The hallmark covers the metal, not what is set in it. A 750 ring with a large stone is 750 gold plus a stone, and the stone is not gold; the guide to stones, clasps and what is not metal covers what is left out of the weight.
• Hollow gold is marked exactly like solid gold. A light, hollow bangle and a heavy, solid one can carry an identical row of marks.
• You do not need a hallmark to sell your own gold. The Hallmarking Act restricts how a business describes an unhallmarked article it supplies or offers to supply, subject to exemptions such as the minimum weights above; it does not stop you sending an unmarked piece to be checked and bought. An unmarked piece is checked before anything is said about its metal.

07

When not to use the scrap route for marked gold

A gold mark tells you the alloy. It does not tell you whether the piece is worth more whole. A jewel signed by a known maker or retailer, a Victorian 15ct brooch, an Art Deco ring or a gold watch by a known maker (working or not) can each be worth considerably more to a collector or a specialist dealer than as metal, and the right route for those may be an auction house.