You turn over an old ring and spot a tiny 375 stamped inside the band. Or you've found 750 on a necklace and have no idea whether it means 18-carat gold. Those little numbers look cryptic, but they're telling you something very specific about the metal.

The short version: 375, 750 and 950 are fineness marks. They show how many parts per 1,000 of the item are pure precious metal. 375 is 9ct gold, 750 is 18ct gold, and 950 is 95% platinum or 95% palladium, so you need the rest of the hallmark to know which. Below, we explain how UK jewellery hallmarks work, what the law actually requires and how to avoid getting caught out when you buy.

A UK jewellery hallmark is an official set of marks struck by an independent Assay Office on gold, silver, platinum or palladium jewellery. It tells you what the metal is, how pure it is and which office tested it. You can't judge any of that by eye or by touch, which is exactly why the system exists.

The rules sit in the Hallmarking Act 1973. As the Assay Offices' own guidance notes explain, the main offence is about description: in the course of trade, you can't describe an unhallmarked article as wholly or partly made of gold, silver, platinum or palladium, unless it falls under one of the exemptions. The guidance says this applies equally to online sellers, market stalls and shops.

In plain English, if a seller calls a piece gold, silver, platinum or palladium and it weighs more than the exemption weight, it should carry a hallmark. We cover the exemptions in detail further down.

These three numbers are the ones UK buyers meet most often. Each one is a millesimal fineness mark, which simply means parts per thousand of pure metal in the alloy.

What Does 375 Mean?

375 means the jewellery contains at least 375 parts gold per 1,000, equivalent to 37.5% gold. In the UK, 375 is the millesimal fineness mark associated with 9-carat gold. The remaining 62.5% is other metals, such as copper or silver, which add strength and help create the colour.

It's also the lowest fineness that can be hallmarked and sold as gold in the UK. So yes, 375 is real gold, just with a lower gold content than 18ct. If you're weighing up the two, our guide to 9ct vs 18ct gold goes through the practical differences.

What Does 750 Mean?

750 means the jewellery contains at least 750 parts gold per 1,000, or 75% gold. In the UK, 750 is the millesimal fineness mark associated with 18-carat gold. The other 25% is alloy metal chosen to give the piece its colour and wearing qualities.

You'll see 750 on a lot of fine jewellery, including diamond engagement rings. It means the same thing on a ring, a necklace or a pair of earrings; only the position of the stamp changes.

What Does 950 Mean?

950 means 950 parts per 1,000 are pure precious metal, so 95%. On its own, the number doesn't tell you which metal. In the UK, both platinum and palladium can be hallmarked at 950, and the shape around the number, plus any traditional symbol, shows which one you have.

This catches out plenty of buyers, so we've given it a section of its own: what 950 means on jewellery.

Divide any fineness mark by 10 and you have the percentage of pure metal. So 375 becomes 37.5%, 750 becomes 75% and 925 becomes 92.5%. Here are the UK fineness standards listed in the official hallmarking guidance notes.

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Carats and fineness marks line up closely but not perfectly. Carats are parts out of 24, so 18ct is 18/24, which works out at exactly 75%. For 14ct, 14/24 is about 58.3%, but the UK hallmarking standard is 585. That's why you'll see both "14ct" and "585" used for the same gold.

A complete modern UK hallmark has three compulsory marks: the sponsor's mark, the fineness mark and the Assay Office mark. They're usually struck side by side in a row, and they're tiny, so a 10x loupe or your phone's camera zoom helps.

Illustrative layout only. The letters and shapes above are not a real registered mark, and genuine hallmarks use official punches. The example reads: a sponsor, 18ct gold, tested at Birmingham.

Sponsor's Mark

The sponsor's mark shows who submitted the piece for hallmarking. In the UK it has at least two letters inside a surround, and no two sponsor's marks are the same at one Assay Office. It doesn't necessarily identify the person who physically made the jewellery.

A manufacturer, importer or retailer can all register as a sponsor. So the letters tell you who took responsibility for sending the item to be tested, not where or by whom it was crafted.

Fineness Mark

The fineness mark is the number that states the metal's purity in parts per thousand, such as 375, 750 or 950. The official guidance notes explain that the number gives the purity and the shape of the surround indicates the metal type. That's how you tell a 950 platinum mark from a 950 palladium one. See the shapes section below.

Assay Office Mark

The Assay Office mark identifies which of the four UK Assay Offices tested and hallmarked the item. It shows where the piece was tested, not necessarily where it was manufactured. A ring made overseas, for example, can be sent to a UK Assay Office and carry its mark. More on this in the next section.

Date Letter

A date letter shows the year the piece was hallmarked. It's optional today, but it was compulsory until 1999. According to the official guidance, the letter changes once a year, on 1 January. The Assay Offices publish date letter tables, and you'll need the right one for the right office, because letter styles and shield shapes differ.

Traditional Fineness Symbols

Traditional fineness symbols are optional pictorial marks that show the metal at a glance. They include a crown for gold, a lion for sterling silver, Britannia for Britannia silver, an orb with a cross for platinum and a helmeted head for palladium. They can't replace the compulsory fineness number; they sit alongside it.

Convention Marks

The Common Control Mark (CCM), often called a Convention mark, is a pair of scales. It's recognised in the UK and in other member countries of the International Convention on Hallmarking, so a piece carrying it doesn't need testing again when sold between those countries. A Convention hallmark has four marks: the sponsor's mark, the common control mark, the fineness mark and the Assay Office mark.

There are two types. Type 1 has the fineness built into the design, with the shape showing the metal. Type 2 shows only the scales, so it needs a separate mark showing the metal and fineness. Either way, the item also needs a sponsor's mark and an Assay Office mark.

There are four Assay Offices in the UK: London, Birmingham, Sheffield and Edinburgh. Each has its own town mark, and the British Hallmarking Council oversees the system. All four apply the same legal standards, so one office isn't "better" than another.

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The mark tells you where the item was tested, which isn't always where it was made. Any registered sponsor can submit work to any of the four offices, so a Birmingham anchor on a ring doesn't mean it was made in Birmingham.

The shape around the fineness number tells you which precious metal the number refers to. This is the quickest way to separate a 950 platinum mark from a 950 palladium one, and a 925 silver mark from a number on a different metal. The official guidance notes include a chart showing each surround.

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The shapes are described in general terms here, because the exact outlines are best checked against the official chart in the Assay Offices' hallmarking guidance notes (PDF). The sponsor's mark also sits inside its own surround, and the Assay Office mark and traditional symbols may have different outlines again.

375 (9ct) gold is 37.5% gold, and 750 (18ct) is 75% gold. 18ct has a higher gold content and generally costs more, while 9ct has a larger share of alloy metals and is often chosen for everyday jewellery. Neither is automatically better. The right choice depends on your budget, how you'll wear the piece, the design and your own preference.

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Which Gold Fineness Should You Choose?

If you're shopping for a ring, browse our diamond engagement rings and wedding rings, where product listings show the metal options available. For a deeper comparison, read our guide to the different types of gold.

950 means 95% pure precious metal, but the number alone doesn't say which metal. In the UK, 950 can be platinum or palladium. To tell which, look at the shape around the number, the traditional symbol beside it and the metal named in the description. Never assume a 950 mark is platinum without checking the complete hallmark.

The reason is simple. The UK hallmarking standards include platinum at 850, 900, 950 and 999, and palladium at 500, 950 and 999. That puts 950 in both lists.

How to Tell Which 950 You Have

If platinum is on your shortlist, our guide to platinum vs white gold covers the differences in look, weight and care. You can also browse platinum engagement rings, platinum earrings and platinum necklaces.

No. A hallmark records fineness, not colour. Yellow, white and rose gold can all carry the same fineness mark: 375 can be yellow, white or rose 9ct gold, and 750 can be yellow, white or rose 18ct gold. The colour comes from the other metals mixed with the gold, not from the hallmark.

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White gold is often finished with a thin rhodium plating for a brighter white, and the official guidance permits rhodium plating on hallmarked gold. The hallmark still refers to the gold alloy underneath. Our guide to what white gold is explains how it's made and cared for.

To see the three colours side by side, try our yellow gold bracelets, white gold earrings and rose gold necklaces.

A hallmark confirms that the hallmarked metal meets the stated fineness, so a 750 hallmark on a ring means that metal is at least 75% gold. It doesn't mean everything attached to the piece is gold. Plating, rolled gold and mixed-metal designs follow separate rules, so read the description as well as the stamp.

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Mixed-metal pieces can be hallmarked too, as long as the precious metal part meets the minimum fineness. If a piece includes base metal parts, the guidance requires the word +METAL to be applied next to the hallmark on the precious metal part, so you may spot that on some designs.

No. Under the Hallmarking Act 1973, items below a set weight don't need a hallmark: 1g for gold, 7.78g for silver, 0.5g for platinum and 1g for palladium. Heavier items must be hallmarked if they're described as made of those metals, though there are other exemptions too, including many pre-1950 pieces.

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The weight counts the total metal weight, including any base metal in the piece. So a small silver charm might be exempt, while a chunky silver bracelet isn't. Many rings, bracelets and pendants weigh more than the gold threshold, which is why you'll usually find a hallmark on them.

Other exemptions exist too. The official guidance lists coins, raw materials, items for dispatch outside the UK and articles too small or thin to be marked, among others. Some older items are exempt as well, which we cover in the vintage section.

No hallmark doesn't automatically mean fake. The piece may be under the legal weight, made before the exemption dates, made abroad under another system or simply worn. But for a modern piece above the weight threshold, sold as gold, platinum, palladium or silver, you'd expect one. Ask the seller to explain.

Common Reasons for a Missing Hallmark

• The item weighs less than the exemption weight for its metal
• It was made before 1950 (or in some categories before 1975), when different rules applied
• It was made overseas and carries a foreign stamp instead of a UK hallmark
• The marks have worn away through years of wear, polishing or resizing
• It isn't solid precious metal, so a gold hallmark wouldn't apply

What to Do Next

Ask the seller for the metal, the weight and clear photographs of any stamps. For an inherited piece, a jeweller or an Assay Office can test the metal, which gives you a definite answer. Don't guess from colour or weight alone, because gold-coloured metal can be gold, plated or something else entirely.

Antique and vintage pieces often carry older marks and sometimes none at all. UK hallmarking has a long history, and the system you see today isn't the one that applied to a Victorian brooch or a 1960s wedding ring. The key rule: don't identify old marks from memory. Check them against published tables or ask a specialist.

What You Might See on Older Pieces

• Date letters. They were compulsory until 1999, so most hallmarked pieces made before then carry one. The letter, its font and the shield around it all matter, and they differ by Assay Office.
• Traditional fineness symbols. Older gold pieces may show a crown, and silver may show a lion. These pre-date the modern millesimal numbers, which is why a very old piece may show only symbols.
• Historic town marks. Some offices have closed, and others changed their marks. Older Sheffield work may show a crown rather than a rose.
• Duty marks. Some Georgian and Victorian silver carries a sovereign's head, which shows that duty was paid. Duty was levied from 1784 to 1890.

Why Some Old Jewellery Has No Hallmark

The official guidance notes explain that before 1975, many articles were exempt, including rings other than wedding rings, and that platinum wasn't hallmarked at all before 1 January 1975. A pre-1950 item can also be described and sold as precious metal without a hallmark, if the seller can prove it's of minimum fineness and was made before 1950.

If you love the character of older jewellery, our guide to vintage-inspired engagement rings is a good starting point, and you can browse vintage engagement rings and antique-style rings to see the look in modern, fully hallmarked form.

A UK hallmark is applied by an independent Assay Office and includes a sponsor's mark, a fineness mark and an Assay Office mark. A foreign stamp, such as 14K, 585 or 925 on its own, is typically a description of the metal rather than a UK hallmark. Convention marks from member countries are the exception: they're legally recognised in the UK.

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Great Britain and Northern Ireland

This part is where the law has changed, so it's worth knowing the headlines. According to GOV.UK, from 1 January 2021 the obligation to recognise equivalent EU hallmarks ended in Great Britain. New stock entering the GB market needs a UK hallmark or a Common Control Mark, while products already on the market before that date remain legal. For the Northern Ireland market, EU hallmarks continue to be recognised.

The UK weight exemptions may also differ abroad. For example, GOV.UK notes that the Republic of Ireland has no exemption weights. If you're buying jewellery from overseas, ask whether it carries a UK hallmark or a Convention mark, and read the GOV.UK guidance on hallmarking and the EU if you need the importer's view.

You don't need specialist kit to do a sensible check. Here's a simple routine that works for rings, chains, earrings and pendants, in a shop or from photographs online.

A hallmark confirms the metal and its minimum purity, which underpins the value of a piece, but it isn't a price on its own. Value depends on how much metal the item contains, its fineness, any gemstones, the design, the maker and its condition. Two pieces with the same 750 hallmark can be worth very different amounts.

Here's the practical effect. Because 750 gold contains twice the proportion of gold as 375, a 750 piece will hold more gold per gram than a 375 piece of the same weight. That's one reason 18ct usually costs more. But a heavy 9ct bracelet can contain more total gold than a delicate 18ct chain, so weight matters as much as fineness.

Hallmarks also help with resale and insurance, because a valuer can confirm the metal quickly. For antique pieces, the sponsor's mark and date letter can add provenance. For diamonds, remember that the hallmark covers the metal only. The stone is graded separately, which is why we recommend reading about GIA graded diamonds and comparing lab-grown diamond engagement rings with natural diamond engagement rings before you decide.

Save or screenshot this cheat sheet for the next time you're squinting at a tiny stamp.

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Read the Whole Row, Not Just the Number

The most useful habit is simple: when you find a hallmark, ask three questions. What metal is it? How pure is it? Who tested it? The fineness number answers the second, the surround and symbols answer the first and the Assay Office mark answers the third.

Once you can answer those, you can spot the difference between a trustworthy listing and a vague one. And if a piece is above the exemption weight but has no marks, or a 950 has no clue about which metal it is, don't be shy about asking. A good jeweller will be happy to explain what you're looking at.