999 on silver is a fineness mark: 999 parts of pure silver in every 1,000, or 99.9%. It is the highest silver standard that any of the systems on this page recognise, and the mark is common on bars, rounds and some jewellery. Like every fineness mark, it says how much of the metal is silver, not who made the piece or what it is worth. This page sets out how the UK, India and the US each treat it, from the rules themselves. It puts no value on any piece.
The arithmetic
Fineness is parts per thousand, so 999 ÷ 1,000 = 0.999. A piece whose silver weighs 31.1034768 g, one troy ounce, and that truly meets the mark contains 31.072 g of pure silver. Sterling at 925 would hold 28.771 g in the same weight. The gap is the other metals that sterling contains and fine silver nearly does not.
In the United Kingdom: one of four silver standards
Schedule 2 of the Hallmarking Act 1973 lists four silver standards: 800, 925, 958.4 and 999. A UK assay office strikes the figures 999 inside the silver shield as the compulsory standard mark. The optional pictorial mark for 999 is “the figure of Britannia or a lion passant”, the same choice the schedule gives the 958.4 Britannia standard, and at the Edinburgh Assay Office the lion passant is read as a lion rampant. The UK hallmark symbols tool shows every standard with its mark.
So a seated Britannia on a modern UK piece does not by itself say 958. It can stand for 999 as well, and the number beside it settles which. The Britannia silver guide explains the older of the two standards. As with all UK silver, a piece of 7.78 g or more needs a hallmark before it may be described as silver in trade, so a 999 inside a full UK hallmark is the assay office’s finding, not the maker’s claim.
In India: new in IS 2112:2025
India’s silver hallmarking standard is IS 2112. A Press Information Bureau release of 4 September 2025 says the 2025 edition has seven purity grades, 800, 835, 925, 958, 970, 990 and 999, and that 958 and 999 were newly added. Under the 2014 edition the highest grade was 990. So an Indian hallmark reading 999 dates from the new scheme, and comes with the three-part mark of that scheme: the BIS Standard Mark with the word SILVER, the purity grade and an HUID code. The silver HUID guide covers the code and the India silver grades tool both lists.
In the United States: the number is the description
US rules have no “fine silver” definition to match “sterling” or “coin”. What they do have matters more for 999. Under 16 CFR § 23.5(b)(1)of the FTC’s Jewelry Guides, using the word “silver” on its own to describe a product is misleading unless an equally conspicuous fineness mark in parts per thousand immediately precedes it. A mark such as “999 silver” is exactly that form: the number is what makes the word acceptable.
The National Gold and Silver Stamping Act, 15 U.S.C. § 296, allows a numbered silver mark to fall short of the number by no more than four parts per thousand on a part tested without solder, and ten across the whole article with solder. For 999 that means 995 and 989. The silver stamp tolerance calculator works out the same figures for any mark. There is no test before sale in the US, so a 999 stamp is the seller’s claim.
999 on bars
In the wholesale market the same figure appears as a floor. The LBMA’s Good Delivery rules for London silver bars set a minimum acceptable fineness of 999.0 parts per thousand, with each bar holding between 750 and 1,100 troy ounces of silver. Retail bars are a different market with their own makers and marks. The silver bar fine weight calculator works out the pure silver in any bar from its weight and fineness.
What a 999 mark does not tell you
- Who stands behind it. A UK hallmark includes a sponsor’s mark and an assay office mark; an Indian one an HUID; a bare US “999” names no one.
- That it is genuine. A number can be struck on anything. The fake hallmark guide covers the signs that a mark does not fit the piece.
- What it is worth. The silver content gives a melt value, which the silver value calculator works out at the live price. A coin or bar may change hands for a different figure, and this site keeps the two apart.
Sources
- Hallmarking Act 1973, Schedule 2, Part I (legislation.gov.uk).
- Press Information Bureau, Ministry of Consumer Affairs, release 2163768 (4 September 2025), on IS 2112:2025, read 20 October 2026.
- 16 CFR § 23.5, FTC Guides for the Jewelry, Precious Metals, and Pewter Industries (Cornell LII), read 20 October 2026.
- 15 U.S.C. § 296, National Gold and Silver Stamping Act (govinfo.gov).
- LBMA, A Guide to the Loco London Precious Metals Market, London Good Delivery: gold and silver.