A piece of British silver stamped 958, or showing a small seated figure of a woman with a shield, is Britannia silver. It is one of the four silver standards UK law recognises, and it is finer than sterling: 958.4 parts of pure silver in every 1,000, against sterling’s 925. This page sets out what the standard is in law, how its marks look, and where it came from, using the Hallmarking Act 1973 and the London Assay Office’s own history. It puts no value on any piece.
The standard in law
Schedule 2 to the Hallmarking Act 1973 lists the standards of fineness the UK recognises. For silver there are four: 800, 925, 958.4 and 999. Britannia is the 958.4 standard. The schedule gives it to one decimal place, which is why references that write it as a plain 958 are rounding.
The same schedule sets the standard mark struck for each fineness. For 958.4 silver the standard mark is “the figures 958”. So the number on the metal is 958 even though the standard behind it is 958.4. On a UK hallmark that number sits inside a shield whose shape signals that the metal is silver; the guide to UK hallmarking explains the shields and the other compulsory marks.
As a fraction, 958.4 parts per thousand is 95.84% silver. The London Assay Office’s history describes the standard in exactly those terms, as plate raised to 95.84% pure silver. The remaining 4.16% is other metal, usually copper, added to make the silver workable.
The Britannia figure
Alongside the compulsory marks, the Act allows an optional pictorial mark for each standard. For 958.4 silver, Schedule 2 names “the figure of Britannia or a lion passant”. Where the Edinburgh Assay Office strikes the mark, the Act reads the lion passant as a lion rampant instead. The same pictorial marks are listed for 999 silver. Sterling, at 925, takes the lion passant (or, in Edinburgh, the lion rampant) but not Britannia.
So a seated Britannia on a modern UK piece points to 958.4 or 999 silver, but it is optional, and its absence proves nothing. The number in the shield is the mark that states the fineness. The London Assay Office notes that it applies the traditional fineness symbol as standard, while describing it as an optional part of the hallmark in general.
Where the standard came from
The London Assay Office gives the origin. In 1697, so much silver coin was being melted down to meet demand for silver plate that the standard for plate was raised to 95.84% pure silver, to protect the coinage from the melting pot. The marks changed with it: a lion’s head erased and a seated figure of Britannia replaced the crowned leopard’s head and the lion passant guardant. The maker’s mark changed too, from initials or devices to the first two letters of the maker’s surname.
The higher standard did not last as the only one. By a statute of 1719, in force from 1720, the old sterling standard was restored, but Britannia remained as an alternative. It has stayed a lawful standard ever since, which is why the 1973 Act still lists it.
Two cautions follow from that history. First, a Britannia figure on a piece from the 1697–1720 period sits within a different set of marks from a modern one, and reading old marks reliably is a specialist subject; this site deliberately does not publish date-letter tables, for the reason given on the assay office marks page. Second, the London Assay Office also records a different figure of Britannia, a standing one, used in 1784–85 to show that a duty drawback had been paid. It was withdrawn in July 1785 because striking it on finished goods caused damage. A Britannia figure on its own is therefore not enough to date a piece.
Britannia and other silver standards
- Sterling, 925. The most common UK standard, and the US definition of sterling under 16 CFR § 23.5 and the National Stamping Act. Britannia contains 33.4 more parts of silver per thousand.
- India’s 958 grade. The BIS standard IS 2112:2025 added a 958 grade; the India silver hallmark grades page covers it. It is written as a whole number and is a separate standard under separate law.
- Britannia coins. The Royal Mint’s Britannia bullion coins share the name and the figure, but a coin is not a hallmarked article. Its fineness is whatever its mint states for that issue, and it need not be the 958.4 standard.
The silver purity by country table sets the UK, US and Indian standards side by side.
What the mark does and does not tell you
A UK hallmark at 958 means an assay office tested the article and found it met the 958.4 standard, since UK assay offices mark a piece to the lowest standard present so that the whole article is at least the fineness shown. It does not say who made the piece, or what anyone would pay for it. For the silver content of a Britannia piece, multiply its weight by 0.9584. The silver value calculator lists 958 Britannia as one of its purities, working from the 958 figure struck on the metal, at the live silver price. That figure is melt value, which is a different number from what a piece of hallmarked silver might be valued at as an object, and the two are kept apart throughout this site.
Sources
- Hallmarking Act 1973, Schedule 2 (legislation.gov.uk): standards of fineness, standard marks and optional pictorial marks.
- The Goldsmiths’ Company Assay Office (London), “History of Hallmarking” and “What is a Hallmark?”.