How to read gold and silver stamps

It started in London in 1300

England's kings were trying to set standards for gold and silver as early as 1238, when Henry III appointed six goldsmiths to oversee the craft.

The big step came in 1300. A law under King Edward I set the sterling standard for silver at 92.5% pure. It also said no silver vessel could leave the maker's hands until it was marked with a leopard's head. It was the first mark English law required.

More marks followed over the next few centuries:

• 1363: the maker's mark. Each goldsmith had to register a personal mark and strike it beside the leopard's head.
• 1478: the date letter. A letter that changed each year showed which official had tested the piece. From then on, Goldsmiths' Hall in London was home to a permanent assay office, or testing office. The word "hallmark" most likely comes from it.
• 1544: the lion. A lion mark, the lion passant, joined the set.
• 1697: the Britannia standard. Silver purity was raised to 95.84%, with a seated figure of Britannia and a lion's head as its marks.

Reading a British hallmark today

A modern British hallmark has three marks that must be there:

• The sponsor's mark. This is the maker's mark: at least two letters inside a shaped border.
• The fineness mark. A number showing purity in parts per thousand, such as 925 for sterling or 750 for 18 carat gold. The shape around the number tells you the metal.
• The assay office mark. This shows where the piece was tested. There are four offices: London, Birmingham, Sheffield and Edinburgh. London still uses the leopard's head.

The date letter is optional today. Very light pieces don't need a hallmark at all: under 1 gram for gold and under 7.78 grams for silver.

Canada's rules

Canada has its own system: the Precious Metals Marking Act and its regulations, overseen by the Competition Bureau. Here's what they say, in plain terms:

• Stamping is optional. Nobody has to put a quality mark on gold, silver, platinum or palladium. But if a mark is there, it has to be true.
• The dealer does the marking. Under the Act, a "dealer" includes makers, importers, wholesalers and retailers. It's their job to get the mark right.
• A trademark has to come with it. If a piece carries a quality mark, it must also carry a Canadian trademark that's registered or applied for. Both have to be put on the same way, so a stamped quality mark needs a stamped trademark. Pieces hallmarked under UK law, or correctly marked under another country's laws, are exempt.
• Gold starts at 9K. A gold quality mark must be between 9 and 24 karats.
• "Silver" means sterling. In Canada, the marks "silver", "sterling", "sterling silver" and .925 all mean at least 925 parts silver per 1,000.
• Platinum and palladium start at 95%. For palladium, that 95% can include a little of certain other precious metals. The marks are "platinum" or "plat." and "palladium" or "pall."

The law also allows a tiny margin. A gold piece can test up to 3 parts per 1,000 below its mark, or 7 parts per 1,000 if it has solder. For silver, it's 2 parts without solder and 6 with.

Gold stamps: karats and numbers

Gold is marked two ways. A karat stamp (K, Kt, C or Ct) tells you how many parts out of 24 are gold. A number tells you the parts per 1,000. Canada's rules list the decimals .375, .416, .583, .750 and .916, and the Competition Bureau also accepts .417 for 10K. Other countries use slightly different numbers for the same karat, which is why you'll see more than one version.

Silver stamps

Here are common silver stamps and what they mean:

• 925, STG or "sterling": sterling silver, 92.5% silver.
• 958.4: Britannia silver, 95.84% silver.
• 999: fine silver.
• 800: 80% silver. It's a legal standard in the UK and Ireland. In Canada, the word "silver" on a piece is reserved for 925.

Plated and filled: marks that mean "not solid"

Some stamps tell you a piece is another metal underneath, with a layer of gold or silver on top. In Canada, the gold layer must be at least 10K. Here's what to look for:

• Gold filled (G.F.). The gold must be at least one-twentieth of the piece's total weight. A typical mark reads "1/20 10K G.F."
• Rolled gold plate (R.G.P.). Same idea, with less gold: under one-twentieth of the weight. A typical mark reads "1/30 10K R.G.P."
• Gold plated, gold electroplate (G.E.P.). A layer of gold over another metal. If the thickness is marked, it must be at least 1 micron.
• Heavy gold electroplate. A U.S. term for a thicker plating layer, at least 2½ microns.
• Vermeil. Gold of at least 10K over sterling silver.
• Silver plate, S.P. and E.P. Canadian marks for silver-plated flatware and hollowware.
• EPNS. Short for electroplated nickel silver. The base metal, nickel silver, is a mix of copper, nickel and zinc and contains no silver. The silver is only the plated layer on top.

Watch the karat number on plated pieces. On gold-filled and rolled gold plate, Canada's rules say a karat mark must come right after a fraction showing how much of the weight is gold. U.S. rules also put the karat in front of the plating term, as in "12K G.E.P." Either way, the karat describes the gold layer only, not the whole piece.

Why a stamp is a clue, not proof

A stamp is a promise made by whoever put it there. There are a few good reasons we never stop at the stamp:

• Unmarked doesn't mean fake. Marking is optional in Canada, so plenty of real gold and silver carries no stamp at all.
• Plated pieces carry karat numbers too. A "10K" next to G.F. or G.E.P. is about the surface layer.
• Marks aren't always right. In 2016, the Competition Bureau tested almost 1,000 pieces at major stores in Vancouver, Toronto and Montreal. It flagged 16 for further testing at the Royal Canadian Mint.
• Foreign marks follow foreign rules. An 800 mark is a legal standard in the UK and Ireland. It's real silver, just not sterling.

Questions people ask