Fineness

How fineness is written

Fineness uses a millesimal number: parts of pure metal per 1,000 parts of the alloy. It is more precise than carat, which is why bullion uses it. The common figures you will see in the UK:

Fineness tells you the fine weight. A 1 oz Krugerrand at 916.7 weighs about 33.93 g so that it still holds one troy ounce of gold; the extra copper makes it harder wearing.

Hallmarks and the four UK Assay Offices

Under the Hallmarking Act 1973 it is an offence for a business to describe an unhallmarked article as gold, silver, platinum or palladium, unless it is exempt. Gold articles under 1 gram are exempt. A UK hallmark has three compulsory parts:

1. the sponsor's mark (at least two letters within an outline, identifying the maker or importer),
2. the fineness mark, a number such as 375, 750 or 916, inside a shape that shows the metal,
3. the Assay Office mark, showing which office tested it.

There are four Assay Offices: London (the Goldsmiths' Company, leopard's head), Birmingham (anchor), Sheffield (rose) and Edinburgh (castle). The approved UK gold standards are 375, 585, 750, 916, 990 and 999.

Why your coins and bars carry no hallmark

The Act exempts any coin that is or was current coin of the UK or another territory, and any bullion. So a Sovereign or a 100 g bar is not hallmarked. Its fineness is struck by the mint or refiner instead, and bars usually come with an assay certificate. That puts more weight on buying from a known source and on checks such as weight and dimensions. Our guide to checking a gold Britannia for fakes covers this.

Fineness and price

Investment gold must be at least 995 for bars and 900 for coins to be VAT exempt in the UK (see VAT on investment gold). Above that line, a 916.7 coin and a 999.9 coin with the same fine weight hold the same gold, so compare them on price per fine ounce. Use the ranking of the cheapest gold coins delivered in the UK to see both side by side.