Where to Find the Stamp

Gold stamps are small, and they live in places that don't get seen. Look inside the band of a ring, on the tiny tag beside a necklace or bracelet clasp, on the loop of a pendant, on the back of a brooch, or along the inside edge of a bangle.

A phone camera on macro mode, or a simple 10x magnifying loupe, will make most stamps readable. Old rings are often worn smooth on the inside, and a ring that has been resized may have lost its stamp altogether when the band was cut.

You may also find letters, initials or small symbols beside the number. These are usually maker's marks — useful for identifying who made a piece, but not a statement about its purity. When it comes to the gold itself, the number is what matters.

What Each Gold Stamp Means

The number stamped on gold is its purity in parts per thousand. 375 means the metal is 37.5% pure gold, which is 9 carat. 585 is 58.5% (14 carat). 750 is 75% (18 carat). 916 is 91.6% (22 carat). 999 is 99.9% pure gold (24 carat). The rest of the metal is an alloy — usually silver, copper or zinc — added for strength and colour.

• 333 = 8ct (33.3% gold). Seen on some European imports.

• 375 = 9ct (37.5% gold). The most common gold in Australian jewellery.

• 417 = 10ct or 10K (41.7% gold). Mostly American pieces.

• 585 = 14ct or 14K (58.5% gold). American and European imports, and some engagement rings.

• 625 = 15ct (62.5% gold). Antique Victorian and Edwardian jewellery.

• 750 = 18ct or 18K (75% gold). Fine jewellery, engagement rings and Italian chains.

• 916 = 22ct or 22K (91.6% gold). Indian and Middle Eastern jewellery, and gold sovereigns.

• 999 = 24ct or 24K (99.9% gold). Bullion bars and coins, and some Asian jewellery.

You'll see "ct" on most Australian and British pieces and "K" (for karat) on American ones. They mean exactly the same thing.

375 — Australia's everyday gold

If you have a drawer of old chains, signet rings and charm bracelets, most of it is probably 375. Nine carat gold is genuine gold — just less of it per gram. It is harder-wearing than higher carats, which is exactly why so much everyday Australian jewellery was made from it.

750 — the fine jewellery standard

Eighteen carat is the standard for quality engagement rings, fine jewellery and many Italian chains. With three-quarters of the metal being pure gold, a 750 piece is worth roughly twice as much per gram as the same weight in 9ct.

585 — mostly imported

Fourteen carat is the everyday gold of the United States and much of Europe, so in Australia you'll mostly find it on pieces bought overseas or inherited from relatives who lived abroad.

916 — 22 carat and gold sovereigns

Twenty-two carat gold is rich in colour and comparatively soft. It is traditional in Indian and Middle Eastern wedding jewellery, and it is also the purity of the British gold sovereign — which is why sovereigns should always be assessed as coins, not lumped in with scrap.

15ct — the antique one most people overlook

Fifteen carat (625) was widely used in Victorian and Edwardian jewellery until Britain dropped it as a standard in 1932. If you find "15" or "625" on a brooch or locket from a grandmother's jewellery box, it is very likely antique — and an antique piece is sometimes worth more as jewellery than as gold. It deserves to be looked at properly before anyone mentions melting it.

The Letters That Mean Very Little Gold

Some markings look official but are actually telling you the opposite of what you hope. These are the ones to know:

• GP or GEP (gold plated, gold electroplated). A very thin layer of gold over a base metal such as brass or copper.

• HGE (heavy gold electroplate). A slightly thicker plating — but still plating.

• RG or RGP (rolled gold, rolled gold plate). A thin sheet of gold bonded to a base metal core. Common on older Australian lockets, watch chains and cufflinks.

• GF or "1/20 12K GF" (gold filled). A thicker bonded layer. The "1/20" means gold makes up one-twentieth of the total weight.

• "18K GP" or "18K HGE". The 18K describes the plating, not the piece. This one catches a lot of people out.

• 925 on a gold-coloured piece. 925 is sterling silver. A gold colour usually means gold-coated silver, sometimes sold as "vermeil".

These pieces may be beautiful, and a few are collectable in their own right. But as gold, most are worth very little — and some are worth nothing at all. We would rather tell you that now than after you've made the trip.

Why So Much Australian Gold Has No Stamp — or the Wrong One

Many people are surprised to learn that Australia has never had compulsory hallmarking. Unlike the United Kingdom, there is no government assay office testing gold and stamping it as proof. In Australia, the purity mark is applied by the maker, and it is voluntary.

That has a few practical consequences:

• Plenty of genuine gold carries no stamp at all. Handmade pieces, older jewellery and pieces made by small workshops were often never marked.

• Stamps disappear. Resizing, repairs and decades of wear can remove a mark completely.

• Stamps can be wrong. A mark can be struck onto anything, and some overseas costume jewellery is stamped "750" or "18K" despite being plated brass.

None of this means you should distrust every stamp. Most are accurate. It simply means a stamp tells you what someone said about the piece. A test tells you what is true.

How a Stamp Is Checked

A professional buyer doesn't take a stamp on faith, and nor should you have to take the buyer's word for the result. Here is what testing involves — and what it can and cannot tell you.

XRF testing

At Miller Hirsch, gold is tested with an XRF (X-ray fluorescence) analyser. The piece is placed on the machine and, within seconds, it reads the metals present and in what proportions. It doesn't scratch, mark or damage the piece. It also identifies platinum, palladium and silver, which is useful when a white metal ring's stamp has worn away. The reading appears on a screen, and you are welcome to watch it.

The piece is then weighed on precision scales, and both results are shown to you. Purity and weight are the two numbers everything else is built on.

What a tester can't see

No test is perfect, and it would be dishonest to pretend otherwise. An XRF analyser reads the metal at and just beneath the surface. With a heavily plated piece, the surface can look better than the core. That is one reason experience still matters: the weight of a piece in the hand, how it has worn at the edges where plating thins, and whether the reading makes sense for what is in front of us.

Acid testing

You may have seen buyers use the traditional method — scratching the piece on a test stone and applying acid. It works, but it marks the piece and gives a less precise answer. If you are attached to a piece, it is fair to ask how it will be tested before anyone starts.

Is gold magnetic? And other home tests

Gold is not magnetic. If a strong magnet grabs your chain, there is base metal inside it. But the opposite isn't true: brass, copper and many plated pieces aren't magnetic either, so a piece that ignores the magnet hasn't proved anything. Home tests can rule gold out. They can't rule it in. We'd gently suggest avoiding home acid kits on anything sentimental.

What the Stamp Means for What You're Paid

Once purity is confirmed, the gold content of a piece is simple arithmetic: its weight, multiplied by its purity, multiplied by the current gold price. We walk through that maths with a real example — and explain why no buyer can pay the full gold price — in How Much Is Your Gold Actually Worth?

Gold content isn't the whole story, though. A signed designer piece, an antique 15ct brooch or a ring set with good diamonds may be worth considerably more intact than as metal. That is what a buy appraisal is for, and it is why we look at every piece individually rather than weighing a bag. You can read more about how gold, diamonds and gemstones are each assessed in our guide to the buy appraisal process.

Answers to Questions You Might Have

What does 375 mean on gold? It means the metal is 375 parts per thousand pure gold — 37.5%, which is 9 carat. The remainder is usually silver and copper.

Is 375 real gold? Yes. Nine carat is a genuine gold alloy, just with less gold per gram than 18ct or 22ct. It is durable and very common in Australian jewellery.

What does 750 mean on gold? It means 18 carat — 75% pure gold. It is the usual standard for fine jewellery and quality engagement rings.

What is 916 gold? It is 22 carat gold, 91.6% pure. You'll find it in Indian and Middle Eastern jewellery and in gold sovereigns.

Is gold magnetic? No. If a magnet grips the piece, it contains base metal. If it doesn't, that alone doesn't prove the piece is gold.

Is gold plated jewellery worth anything? As gold, very little. Only a microscopically thin surface layer is gold. Some plated pieces have value as vintage or designer jewellery, but not for their metal.

Can a gold stamp be fake? Yes. Because hallmarking isn't compulsory in Australia, a stamp can be applied to anything. That is why every piece should be tested — and why you should be allowed to watch it happen.

What to Do Before You Sell

You don't need to become an expert in gold stamps before you sell. But a few minutes of preparation will help:

• Bring everything. Stamped, unstamped, broken and "probably fake" — let it be tested rather than guessed.

• Don't clean aggressively or test at home with acid. Neither changes the value, and both can do harm.

• Take a photo of the stamps. If you'd like a realistic idea before you visit, send us photos and we'll give you an honest indication.

• Bring current photo ID if you plan to sell. A driver's licence is fine. You don't need ID just to have your pieces assessed.

The stamp starts the conversation. The test finishes it — on screen, where you can see it.

If you're thinking of selling, you can find out more about how we buy gold in Sydney.

Book your free buy appraisal with Miller Hirsch today — no obligation, no pressure, and every test result shown to you live on screen.