Reading Jewelry Hallmarks: A Practical Guide

The marks stamped inside a ring are not decoration. They are a claim about what the metal is, and in the United States the law attaches conditions to making that claim.

Most pieces carry two things: a quality mark saying what the metal is, and a maker's mark saying who stands behind it. Learning to read the first takes about a minute. The second is what turns a piece from anonymous into traceable.

What do the numbers mean?

They are the same fact written two ways.

American pieces usually state gold content in karats, out of 24. British and European pieces usually state it in parts per thousand, which the trade calls millesimal fineness. They convert directly:

• 10K is 417, meaning 417 parts gold per thousand
• 14K is 585
• 18K is 750
• 22K is 916
• 925 is sterling silver, 925 parts silver per thousand
• 950 on a white metal is usually platinum, and often sits next to PLAT or PT

So a ring stamped 750 and a ring stamped 18K are making the identical claim. One was written for a market that thinks in karats and one for a market that thinks in thousandths.

A mark reading 14K GF, GP, HGE or RGP is not a claim about solid gold. Those denote gold filled, gold plated, heavy gold electroplate and rolled gold plate, which are layers of gold over a base metal.

What does the law require alongside the number?

A name, and it has to be next to the number.

Under the National Stamping Act, anyone who applies a quality mark indicating gold or silver content, or imports an article carrying one, must also apply their trademark or name to that article. The law is specific about how: by the same means as the quality mark, in lettering at least as large, and as close as possible to it (15 U.S.C. 297).

This is why a mark like "14K" sitting alone, with no maker's mark anywhere near it, is worth a second look. It does not prove anything is wrong. Plenty of older pieces predate the requirement, and marks wear away over decades of contact with skin. But a modern piece making a metal claim with nobody's name attached to it is a piece where nobody has accepted responsibility for the claim.

How exact does the mark have to be?

Close, and the tolerance is written down.

For gold, the actual fineness may not fall short of the marked fineness by more than three parts per thousand when tested without solder. Once solder is included, the allowance is still three parts per thousand for watchcases and flatware, and seven parts per thousand for other articles, which is a nod to the fact that a soldered joint is a different alloy from the metal around it (15 U.S.C. 295).

In plain terms: an 18K ring may test very slightly below 750 and remain lawfully marked, and a piece with several soldered joints has a little more room. A stone that tests at 14K while stamped 18K is not within any tolerance. It is mismarked.

What is a British hallmark, and why does it look so busy?

Because it is several separate statements struck side by side.

A UK hallmark carries three compulsory marks: the sponsor's mark, which identifies the person or company that submitted the article, the millesimal fineness mark, which gives the metal content in parts per thousand inside a shield whose shape identifies the metal, and the assay office mark, which says which office tested it. London's is a leopard's head. Two further marks are optional: the traditional fineness symbol, and the date letter, which changes every January (Goldsmiths' Company Assay Office London).

That date letter is the reason British pieces can often be dated to the year, which American pieces usually cannot. If you have inherited something with a row of small shields inside the band, you are holding more information than most estate jewelry carries.

What if there is no mark at all?

It tells you less than people assume.

Unmarked does not mean fake, and marked does not mean genuine. Marks wear smooth. Rings get sized, and a sizing cuts out the section of shank where the mark used to be. Older American work was often unmarked. Meanwhile a stamp is just a stamp, and applying a false one is not difficult.

Which is why the mark is a starting point rather than a verdict. A jeweler confirms metal content by testing it, and testing takes minutes. If the mark and the test disagree, the test wins. We have written separately on what an unmarked piece is really worth.

What should I do with a piece I cannot read?

Photograph the marks before anything else. A phone camera held close, with the band against a plain background and good light, captures more than the eye does, and it gives you something to compare against reference charts.

Then have it tested rather than guessing. Metal content, whether the marks match the metal, and whether the maker's mark belongs to someone worth knowing about are three different questions, and the last one occasionally matters more than the first two together.

Bring the piece in and we will read the marks with you and test the metal, at no charge. See what we look for in estate pieces, or book a verbal appraisal.