What Does 585 Mean on Gold? (And 375, 417, 750, 916)

You turn a ring or a chain over and find a tiny number: 585. No "K," no word "gold," just three digits. Is it a model number? A date? A secret code?

It's none of those. In this guide I'll show you what that number means, how it lines up with the karats you already know, and why an older American "14K" piece may hold a little less gold than a new one.

Two ways of counting the same gold

Gold marks come in two languages, and they say the same thing.

Karats divide the metal into 24 equal parts and tell you how many of them are gold. 24K is pure gold. 18K is 18 parts gold and 6 parts other metals. 14K is 14 parts gold and 10 parts other metals.

Three-digit numbers count in thousandths instead. This is called millesimal fineness. A stamp of 750 means 750 parts out of 1,000 are gold, or 75%.

Here are the numbers you're most likely to find, with their karat match:

• 375 = 9 karat = 37.5% gold
• 417 = 10 karat = 41.7% gold
• 585 = 14 karat = 58.5% gold
• 750 = 18 karat = 75% gold
• 916 = 22 karat = 91.6% gold
• 999 = 24 karat = 99.9% gold

These are official standards, not maker's codes. In Britain, the official gold fineness marks are 375, 585, 750, 916 and 999. Italian law sets 750, 585 and 375 as the legal gold finenesses for jewelry, and allows anything purer than 750 too. So when you see one of these numbers on a gold-colored piece, read it as a purity mark.

Why mix gold with other metals at all? Pure gold is very soft. Silver, copper, zinc and other metals make it tougher, and they also change the color. That's where yellow, white and rose gold come from. It also means color tells you nothing about karat: white, yellow and rose gold can all be 14K.

One more spelling note. The British write carat, so "18ct" means the same as "18K."

Why 585, and not 583?

Here's a small puzzle that catches sharp eyes. Fourteen twenty-fourths works out to 583.3 thousandths. So why does the stamp say 585?

Because 585 is the fineness standard used for 14K in the three-digit system. The practical result is good news for you: a piece stamped 585 promises slightly more gold than the karat arithmetic requires.

The pre-1981 American "half-karat" allowance

American law has never demanded perfection to the last speck. Solder, the metal that joins links and parts, is often a little different from the main piece, and the law allows for that.

Under the 1906 Stamping Act as it stands today, the gold itself may fall short of its stamp by no more than 3 parts per thousand. Tested together with its solder, a ring or chain may fall short by no more than 7 parts per thousand. By our own arithmetic, a ring stamped 14K must come to about 576 thousandths or better, solder and all.

It wasn't always that tight. The 1906 law originally allowed half a karat, and a full karat when the whole article was tested with its solder. In 1976, Congress replaced those allowances with the thousandths-based rule, and gave the industry five years. The tighter rule took effect in 1981.

So an American piece stamped "14K" before 1981 could legally have been about 13½ karat: by our arithmetic, about 56.25% gold rather than 58.3%. If a jeweler finds an older American piece slightly under 14K, this may be part of the reason. It doesn't mean anyone cheated your grandmother.

Two related rules worth knowing

Under the FTC's Jewelry Guides, the word "gold" alone means 24 karat, so anything less should carry a karat mark. And since the FTC revised its Guides in 2018, solid gold under 10 karat may be called gold as long as its karat is stated accurately. So a 375 (9K) piece isn't automatically suspect. The 10-karat minimum still applies to the gold layer on plated and covered pieces.

What a three-digit number can't tell you. A stamp is a claim, not proof: it can be wrong or dishonest. It doesn't tell you whether the piece is solid or hollow, or how much gold it holds by weight once stones and other parts are counted. And if you see letters or a fraction beside the number, such as GF, RGP, HGE or 1/20, stop: the piece is probably layered gold, not solid.

Volume I, Real or Fake?, covers every common gold and silver mark, the plated and filled marks that fool so many families, British, European and Mexican hallmarks, the maker's mark that should sit beside the number, and the home tests in the safe order, each with what it can't prove.