How to Read Jewelry Hallmarks and Stamps
That tiny stamp inside a ring tells you what the metal is and who made it. Here is how to decode the numbers and marks on gold, platinum and silver jewelry.
Turn a ring over and look closely and you will usually find a set of tiny stamps, often needing a loupe to read. Those marks are the jewelry's identity papers: they tell you the metal and its purity, and often who made it. Learning to read them takes five minutes and can save you from overpaying or buying a misrepresented piece.
Two systems: karat and fineness
Precious-metal marks come in two flavors, and you will see both.
- Karat marks describe gold purity out of 24: 10K, 14K, 18K, 24K.
- Fineness marks describe purity in parts per thousand, a number stamped without a letter.
They map directly onto each other:
- 999 or 995 = platinum (99.9% or 99.5%)
- 950 = platinum (95%), the common jewelry standard, often stamped PLAT or PT950
- 750 = 18k gold (75%)
- 585 = 14k gold (58.3%)
- 417 = 10k gold (41.7%)
- 925 = sterling silver (92.5%), often stamped STERLING or STER
So a ring stamped 585 is 14k gold, and one stamped 925 is sterling silver. Memorize those few numbers and you can decode most jewelry on sight.
The maker's mark
Alongside the purity stamp you will often find a maker's mark or hallmark: a small logo, set of initials, or symbol identifying the manufacturer or designer. A purity number paired with a registered maker's mark is a good sign of a legitimate, accountable piece. A purity number with no maker's mark at all is not automatically fake, but it is worth a second look.
What the marks do and do not guarantee
Here is a crucial point many buyers miss. In the United Kingdom, hallmarking is legally mandated: qualifying precious-metal items must be tested and stamped by an independent Assay Office, so a UK hallmark is an official, third-party guarantee of purity.
The United States works differently. There is no independent assay office. American marks are largely self-applied by manufacturers under federal stamping and disclosure laws. That means a US stamp is a claim by the maker, backed by law against fraud, but not verified by an outside authority the way a British hallmark is.
The practical implication
Because US stamps are self-applied, the mark is only as trustworthy as the seller. For any significant purchase, buy from a reputable jeweler, and for high-value pieces consider an independent appraisal or testing rather than relying on the stamp alone.
Common extra marks
You may also spot:
- GF or 1/20 12K GF: gold-filled, a thick layer of gold bonded over base metal, not solid gold.
- GP or HGE: gold-plated or heavy gold electroplate, a thin gold coating.
- RHODIUM or no mark on white gold: remember white gold is usually rhodium-plated.
- Vermeil: sterling silver with a gold coating.
Knowing these prevents the common mistake of paying solid-gold prices for a plated or filled piece.
The stamp is the fastest way to know what you are holding. Learn the handful of fineness numbers, look for a maker's mark, and remember that in the US the stamp is a claim, not an official guarantee.
The takeaway
A jewelry stamp encodes the metal, its purity, and often its maker. The key numbers are 750, 585, 417 for gold, 950 for platinum, and 925 for silver. Pair the purity mark with a maker's mark for confidence, watch for plated and filled markings like GP and GF, and remember that American stamps are self-applied, so buy from sellers you trust.