What does 750 mean on a watch?

Search the question and the same line comes back from forum threads and jeweler blogs: 750 means 75 percent gold. That is right, and it is where they stop. In law, a watch case is not a ring. The US statute on gold marks names the watchcase and gives it a tighter tolerance. Switzerland makes the hallmark compulsory on watch cases and on nothing else. Below, those rules sit beside the UK's and the Vienna Convention's, with every number on a case back translated.

What 750 means

Fineness is the share of pure precious metal in an alloy, counted in parts per thousand. Swiss law defines it as "the purity of precious metal contained in a unit of weight of a metal alloy, measured in parts per thousand." So 750 means 750 parts of pure gold in every 1,000 parts by weight. The other 250 parts are other metals, which set the color and hardness, as our guide to watch case materials explains.

Karat counts the same thing in 24ths. 18 karat is 18/24, which is exactly 750/1000. On the same scale 999 is about 24 karat, 916 is 22, 585 is 14, 417 is 10 and 375 is 9. A case stamped 750 and a case stamped 18K make the same claim, and a specification sheet may print either.

Three more terms matter on a case back:

• Fineness mark. The number itself: 750, 585, 950.
• Responsibility mark. A mark that names the maker or firm standing behind the number. The UK calls it the sponsor's mark.
• Hallmark. A mark struck by an independent assay office after it has tested the metal. A 750 on its own is a claim. A 750 beside an assay office mark is a tested claim.

One 750 case under three rules

Take an 18K case whose metal weighs 30 grams, stamped 750, and walk it through each rule. The 30 g is an example, not a typical case.

• At exactly 750, the case holds 22.5 g of pure gold.
• Sold in the US. A piece cut from the case with no solder on it may test as low as 747. Melt the whole case with its solder and it may also test as low as 747. That is 22.41 g, so the law allows 0.09 g less gold than the mark says. If the same 30 g of metal were a brooch, the whole-article test would accept 743, or 22.29 g.
• Sold in Switzerland. The case must go to an assay office before it leaves the case maker. Every part must be at least 750. If the office has allowed a lower-grade solder, the fully melted case may be up to 10/1000 under, so 740.
• Sold in the UK and described as gold. It needs a hallmark. The alloy must be at least 750, and because it is a watch case it may be joined with 740 solder.

So the US lets the alloy itself be slightly under the mark. Switzerland and the UK let only the solder be.

The US rule: 3/1000 for a watchcase

The National Gold and Silver Stamping Act of 1906 (15 USC 294 to 300) does not make anyone mark gold. It makes a wrong mark unlawful. Section 295 sets two tests, and a gold article has to pass both.

1. Parts without solder. The piece taken for testing must not contain solder. Its fineness may be no more than three one-thousandth parts below the mark. This applies to every gold article.
2. The whole article. All the gold, alloy and solder are "assayed as one piece". The result may be no lower than the mark "by more than three one-thousandth parts, in the case of a watchcase or flatware, or than seven one-thousandth parts, in the case of any other such article".

The watchcase rule is the older of the two. Before the Gold Labeling Act of 1976 (Pub. L. 94-450), the general limits were half a karat for a part and one karat for the whole. That is about 21/1000 and 42/1000. Watchcases and flatware already had a 3/1000 exception. The 1976 Act brought everything else much closer. It took effect five years after it was passed, on 1 October 1981, and does not apply to articles a maker or importer sold before then.

Silver has its own section. Under 15 USC 296, silver may be no more than 4/1000 below its mark. The Act does not cover platinum. For that, the FTC's jewelry guides say "Platinum" without qualification means 950 parts per thousand. Their scope names watch bands that are not permanently attached, but not watchcases. The same guides list "9 Karat Gold" as an acceptable mark, so 375 is lawful gold in the US.

Nothing in the Act sends a case to a laboratory before sale. The mark is the maker's or importer's claim, and the Act is the standard it is judged by afterwards. Our answer on what gold filled means on a watch covers the cases that only have a layer of gold.

Switzerland: every gold case is hallmarked

Switzerland is the country where the watch case is the whole point. Its customs office, which runs precious metals control, says: "All watch-cases in gold, silver, platinum or palladium, of foreign or local manufacture, sold in Switzerland, are subject to control and compulsory official marking." For all other precious metal articles, the control is optional.

The Precious Metals Control Act (SR 941.31) and its ordinance (SR 941.311) say what that involves:

• When. A precious metal case "may not be placed on the market" before it is tested and hallmarked. It counts as on the market "as soon as" it leaves the case maker's plant. Cases made for export, at the fineness the buyer's country requires, are covered too. Cases sent straight to a country that runs its own compulsory case control may skip the Swiss hallmark.
• The hallmark. One official mark for every metal and fineness: the head of a St Bernard dog, carrying the symbol of the assay office that did the test.
• The number. Fineness goes on in parts per thousand, "in Arabic numerals", at least 0.5 mm high. A karat mark such as 18K may be added if it is true. Platinum and palladium marks must also name the metal, for example "Pt".
• Who stands behind it. A fineness mark may not go on without a responsibility mark. For watch cases, members of a makers' association may use a shared responsibility mark with a serial number.
• How close. "All parts of a precious metal article must at least meet the specified fineness." The ordinance's only fineness tolerance is for solder. Solder should in principle be the same alloy as the case. Where the office allows a lower one, the fully melted object may be up to 10/1000 under.

Swiss legal standards for gold are 999, 916, 750, 585 and 375. For platinum they are 999, 950, 900 and 850, and for silver 999, 925 and 800. There is no 417, so 10K is not a Swiss standard. A plated case is a different article. Swiss gold plating must be at least 5 micrometres of at least 585 gold. A gold-capped case ("coiffe or", marked GC) needs at least 200 micrometres. None of this is the "Swiss made" origin rule, which our answer on what Swiss made actually means covers, along with our guide to Swiss origin marks.

The UK: no hallmark, no "gold"

In the UK the rule turns on words. The guidance notes from the four UK assay offices (November 2022) say the main offence under the Hallmarking Act 1973 is "based on description". In trade, it is an offence to describe an unhallmarked article as wholly or partly gold, platinum, palladium or silver, or to supply one described that way. That covers online sellers and pre-owned items, which matters when selling a watch. A maker's fineness mark counts as a description.

• Exemptions. Gold under 1.0 gram is exempt. For an article of precious and base metal, the weight counts all the metal, base metal included. Platinum's limit is 0.5 g and silver's 7.78 g. An item made before 1950 may be sold as gold without a hallmark if the seller can prove its fineness and its age.
• The watch case concession. The table of standards lists 750 gold for a "Filigree or watch case" with 740 solder. Other 750 work uses 750 solder.
• Other solders. 999 and 916.6 gold use 750 solder. 585 uses 585 (500 for white gold), and 375 uses 375. 925 silver uses 650, and 950 platinum needs precious metal of at least 950.
• The hallmark. Three compulsory marks: sponsor's mark, metal and fineness mark, assay office mark. The fineness mark says the metal is "not less than" the number. The date letter has been optional since 1999.
• The "gold watch" trap. If a base-metal watch with no gold is called a "gold watch" to describe its color, that "would constitute an offence". The guidance suggests "yellow metal watch", "gold tone watch" or "gold coloured watch" instead. Our guide to watch marketing claims covers these phrases.

UK standards for gold are 999, 990, 916.6, 750, 585 and 375. There is no 10K here either: bonded gold "of 10k can only be described as 9 carat in the UK."

The Vienna Convention's Common Control Mark

The Convention on the Control and Marking of Articles of Precious Metals, often called the Vienna Convention, lets its members accept each other's hallmarks. Its sign is the Common Control Mark, a pair of scales. Since Italy joined on 15 December 2023 it has 22 contracting states: Austria, Croatia, Cyprus, the Czech Republic, Denmark, Finland, Hungary, Ireland, Israel, Italy, Latvia, Lithuania, the Netherlands, Norway, Poland, Portugal, Serbia, Slovakia, Slovenia, Sweden, Switzerland and the UK. The US is not a member.

A Convention hallmark has four parts: sponsor's mark, Common Control Mark, fineness mark and assay office mark. On type 1, the fineness is built into the scales and the outline shows the metal. Type 2 shows the scales only, so the metal and fineness must be marked beside it. The Convention recognizes gold at 375, 585, 750, 916, 990 and 999, platinum at 850, 900, 950 and 999, and silver at 800, 925, 958 and 999. In the UK, an article with a Convention hallmark does not have to be hallmarked again.

Membership does not make hallmarking compulsory. The Convention's country profiles show "Voluntary" for Austria, Finland, Italy and Norway, and "Compulsory" for the UK, Ireland and Portugal, among others. Switzerland's reads "Compulsory for watch-cases; Voluntary for jewellery". For watch cases only, Switzerland also accepts the marks of the assay offices of Spain, Austria, Russia and Kazakhstan. The profiles are for information only and have no legal status.

Every number translated

Reading a 750 on a case back

1. Find the mark beside the number. In Switzerland and the UK, a fineness figure comes with a responsibility or sponsor's mark.
2. Look for an assay office mark. A St Bernard dog's head, a British assay office town mark or the Convention's scales means the metal was tested.
3. Do not read a listing as a mark. The number also turns up in model names, such as Doxa's Sub 750T, where it is not a fineness mark. The Swiss and UK rules put the number on the article itself.
4. Check for plating marks. GC with a micrometre figure on a Swiss case means a gold layer, not a gold case.

Our guides to spotting a fake watch, buying pre-owned and buying vintage cover what to check next. Gold content is not a price: a gold watch is valued as a watch, as our answer on finding out what a watch is worth sets out. And insure it as what the marks say it is.

When this answer stops applying

• The watch is sold somewhere else. Only US, Swiss and UK law and the Convention's profiles were read for this page. Other countries have their own rules. Bringing a gold watch home from abroad raises a separate question, covered in our answer on duty on a watch bought abroad.
• The case predates the rules. The 7/1000 limit for other gold applies to articles sold from 1 October 1981. The Swiss texts were read in their current English versions, which have no legal force; the German, French and Italian texts are the law.
• The mark itself is in question. A mark is only as good as whoever struck it. This page says what a genuine mark promises, not whether the one in front of you is genuine.
• It is not the case. The US whole-case test covers the gold, alloy and solder. Swiss law lets mechanisms and other parts be of other materials where technically needed. A 750 case says nothing about the movement or crystal inside.

Otherwise: 750 is 18K, 75 percent gold. A US watchcase may test no lower than 747, Switzerland hallmarks every precious metal case, and the UK lets a 750 watch case use 740 solder.