A UK ring with a platinum head on a gold shank, or a silver bangle with gold details, can carry more than one fineness number. That is not a mistake or a sign of tampering. Since a 2007 amendment to the Hallmarking Act, articles made of more than one precious metal can be hallmarked as one piece, under conditions the four UK assay offices set out in their Hallmarking Guidance Notes (November 2022). This page summarises those conditions. The notes themselves say they should not be relied on as a legal interpretation, and neither should this page; it puts no value on any piece.
Two conditions before anything is struck
An article of more than one precious metal can only be marked if, in the opinion of the assay office, an ordinary person will be able to tell which part is which metal. A design where platinum and white gold are indistinguishable to the eye fails that test.
Each precious metal part must also be at least the minimum legal fineness for its metal: platinum 850, gold 375, palladium 500 and silver 800 parts per thousand. A part below its minimum is not that precious metal for hallmarking purposes.
Two standards of the same metal are not mixed metals. A piece combining 375 and 750 gold receives the hallmark for the lower standard, 375. The whole article is marked at the fineness it can guarantee throughout.
Which full hallmark, and where
The full hallmark (sponsor’s mark, assay office mark and fineness mark) is that of the least precious metal, taking the order silver, palladium, gold, platinum. It is normally struck on that metal, though if that is not practicable it may go on the more precious one.
The more precious metals then receive their fineness mark only, struck on those parts. So a gold ring with a platinum setting carries the full hallmark for the gold and a platinum fineness mark on the platinum. That is the usual reason for seeing two numbers on one ring.
Small components can make this impossible, and the notes give fallbacks in order. The fineness marks for the higher metals may be struck on the lower metal; failing that, on another precious metal part; and failing both, only the full hallmark of the least precious metal is struck on its part and the other marks are omitted. One further exception covers platinum articles with small parts of gold that is not white gold and is 750 or higher: the piece may take a platinum full mark plus the gold fineness mark anywhere on it, provided the gold parts are no more than half the article’s weight. That exception does not apply to 585 or 375 gold parts.
The weight that triggers hallmarking
UK hallmarking applies above set exemption weights: 0.5 g for platinum, 1 g for gold and palladium, and 7.78 g for silver. For a mixed article, the notes apply the exemption weight of the higher precious metal to the total weight of all the precious metal. Their worked example is a piece with 0.5 g of gold and 3 g of silver: the higher metal is gold, so the threshold is 1 g, and the total of 3.5 g exceeds it, so the article is not exempt, even though neither metal on its own would need marking. The hallmark exemption weights tool applies the same rule.
Precious metal with base metal: +METAL
An article can also combine a precious metal with base metal, such as steel, titanium or brass. The notes allow it to be hallmarked if the base metal parts are clearly distinguishable from the precious metal by colour or texture and clearly visible by their extent. The hallmark goes on the precious metal part only, with the word +METAL struck beside it, and wherever practical the word METAL or the name of the metal is also struck on the base metal part. If a piece has more than one precious metal as well as base metal, the mixed precious metal rules above apply too.
Hidden base metal is treated separately. Small parts such as springs in clasps can be ignored. Larger concealed parts, like a continuous steel spring or wire inside a bangle, are marked +SPRING beside the hallmark, must be no heavier than the technical function needs, and may not exceed half the article’s weight. If such a part is visible by its extent, the piece is treated as precious and base metal and marked +METAL.
Precious metal with other materials
For pieces that combine a precious metal with other materials rather than base metal, the notes require the other material to be clearly distinguishable, not plated to resemble a precious metal, and visible in its extent. The precious metal part must be at least 100 micrometres thick, and it is hallmarked on its own as if it were a separate article.
What is not a mixed-metal article
Plated pieces are not covered. The notes say gold-plated silver is hallmarked as silver and is outside the mixed-metals amendment; the silver gilt guide covers how it is described. Gold plating on base metal cannot be hallmarked at all. For bonded gold, the gold layer must be at least 375 and of a fineness recognised in the UK, so the notes say 10k bonded gold can only be described as 9 carat there.
Reading two numbers on one piece
If a UK piece shows one full hallmark and a second number on its own, the full hallmark belongs to the least precious metal and the lone number to the more precious part. The shield shape around each number identifies the metal; the UK hallmark symbols tool lists every standard and its optional symbol, and the guide to UK hallmarking explains the compulsory marks. For melt purposes each metal has to be weighed separately, which on a finished piece is rarely possible, and melt value is not the same as what a piece is worth as an object.
Sources
- UK Assay Offices, Hallmarking Guidance Notes (November 2022, published on GOV.UK): “Can I use more than one precious metal in one article?”, “Can I use non-precious metals in combination with precious metals?”, “Hallmarking gold plated silver articles” and “Guidance on describing precious metals”.
- Hallmarking Act 1973, Schedule 1 (legislation.gov.uk), for the exemption weights.