333 Gold: What the 8 Karat Stamp Means on Jewelry

In a genuine fineness mark, 333 means 333 parts gold per 1,000 parts alloy, or 33.3% gold. That is the proportion of 8-karat gold. It is a legal gold standard in Germany, Poland, and Denmark, but it is below the lowest gold standard a UK assay office can hallmark.

• That the stamp is genuine or that the piece was independently tested
• That the piece can be sold as gold in every country
• The maker, age, gemstone identity, or value

1. 1Photograph the 333 together with every mark beside it, including any maker’s mark or national hallmark
2. 2Note where the piece was bought or made, because the legal reading of 333 depends on the market
3. 3Ask for an XRF reading when a sale, insurance claim, or scrap offer depends on the gold content

What a 333 stamp claims

333 is a millesimal gold mark: 333 parts gold in every 1,000 parts of alloy, or 33.3 percent. In karat terms that is 8 karat, because 8 of 24 parts is one third. You may see it as 333, as 8K or 8kt, or inside a national hallmark.

The other two-thirds of the alloy is a different metal, and the stamp does not name it. That majority largely sets the color, the hardness, and how the piece wears. A 333 ring and a 750 ring can look alike in a photograph while holding very different amounts of gold.

Like every stamp, 333 is a claim made by whoever struck it. It is stronger evidence beside a registered maker’s mark or an official hallmark, and weaker when it stands alone on a piece with no history.

Where 333 is a legal gold standard

Germany: the German law on the fineness of gold and silver wares allows gold and silver articles to be made and sold in any fineness. For jewelry it says pieces may be stamped in any fineness, stated in thousandths. A 333 stamp on German jewelry is therefore a lawful fineness statement, not a sign of a fake. The same law sets a higher threshold, 585, for stating fineness on other gold articles, but jewelry has its own rule.

Poland: 333 is one of the current Polish gold standards. Polish hallmarks show the standard as a digit, and the Warsaw district assay office lists the digit 6 for 0.333 gold, alongside 0.375, 0.500, 0.585, 0.750, 0.960, and 0.999.

Denmark: Danish precious-metals law requires every precious-metal part of a gold article to contain at least 333 parts per thousand gold, unless the article can be lawfully sold as precious metal in another EU or EEA country or a Convention state. Articles sold as gold must carry a fineness mark in parts per thousand and a registered maker’s name mark. Gold articles under 1 gram are exempt from the marking requirement.

What 333 cannot carry is the international Convention hallmark. The Hallmarking Convention’s Common Control Mark covers gold at 375, 585, 750, 916, and 999, so an 8-karat piece sits below every Convention gold standard.

333 gold in the United States

The FTC Jewelry Guides treat the unqualified word gold as meaning 24 karat. A gold alloy may be called gold only when a correct karat designation immediately precedes the word and is just as conspicuous, and the current Guides give “9 Karat Gold” as an acceptable example. On that reading, an 8-karat piece has to be described as 8 Karat Gold or 8K, never simply as gold.

That is a change. The version of the Guides in force before the 2018 revision listed any use of the word gold, or of a karat mark such as 9 karat, on an alloy below 10 karat as an example of a misleading description, so references written before then give 10K as the minimum for gold. Read 333 on a piece sold in the United States as an 8-karat claim and check that the seller’s description says so.

The 10-karat floor has not disappeared from the Guides altogether. Their examples of acceptable gold plate, gold filled, rolled gold plate, and gold electroplate markings all specify a gold layer of at least 10 karat, and the definition of vermeil does too. A 333 alloy cannot be the gold layer of a product sold under those names.

Why 333 cannot be hallmarked in the UK

Guidance from the British Hallmarking Council states that the fineness of gold articles ranges from 375 (9 carat) to 999 (24 carat). The Birmingham Assay Office lists its gold standards as 375, 585, 750, 916, 990, and 999. 333 is below the lowest of them, so a UK assay office cannot hallmark an 8-carat article as gold.

That matters at the counter. The Hallmarking Act 1973 makes it an offence for a trader to describe an unhallmarked article as gold, or to supply or offer to supply one so described, subject to the Act’s exemptions. The Act’s weight exemption for small gold items applies only to gold of minimum fineness, and the lowest gold standard in the Act is 375. The Act does allow a description confined to the color of an article.

So a 333 stamp on a piece in a UK shop is not part of a UK hallmark. It is a fineness claim from another marking system, and the piece should not be described or priced as 9-carat gold.

333 compared with 375, 417, and 585

The neighboring gold standards each have their own page: 375, 417, and 585. The differences in gold content are large at the low end of the scale. A 585 piece holds three quarters more gold than a 333 piece of the same weight.

• 333 (8K): 33.3% gold. Legal in Germany, Poland, and Denmark; not a UK or Convention standard.
• 375 (9K): 37.5% gold. The lowest UK hallmarking standard and the lowest Convention gold standard.
• 417 (10K): 41.7% gold. The karat the pre-2018 FTC Guides treated as the floor for gold claims.
• 585 (14K): 58.5% gold. A legal standard in every Convention state, and the lowest fineness German law allows to be stated on gold articles other than jewelry.

Testing and valuing a 333 piece

A stamp cannot tell you whether the metal meets 333. The usual non-destructive test is X-ray fluorescence (XRF), which the Birmingham Assay Office uses to verify the proportion of gold in an alloy before hallmarking. XRF reads the area under its beam, so ask which part was tested and have clasps and repairs tested separately.

For value, the starting point is the weight of gold the piece actually contains: a third of the metal weight, if the 333 claim is accurate. That makes a 333 piece worth less in metal than the same weight of 9K, 10K, or 14K gold, but it does not make it worthless, and design, gemstones, condition, and maker can matter more than the metal. The jewelry value guide explains how to build a defensible range, and how to tell if gold is real covers the checks to run first.