Gold jewelry marks: what 14K, 585, 750, GF and HGE mean

A karat stamp such as 14K or a number such as 585 means the metal is solid gold alloy of that purity. Letters such as GF, RGP, GP, GEP or HGE mean a layer of gold over a base metal. The numbers are simple arithmetic: karat divided by 24, in parts per thousand.

By the Antique ID team · Updated 2026-10-13

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Karats and parts per thousand

Pure gold is 24 karat. A karat number tells you how many parts in 24 are gold, so 18 karat is 18/24, or 75% gold. The rest of the alloy is usually silver, copper, zinc or nickel, which change the color and make the metal harder. European and British jewelry usually shows the same information as a three-digit number in parts per thousand.

The figures in the second column are simple arithmetic. The UK dealer's notice published by the British Hallmarking Council lists 9, 14, 18 and 22 carat among the gold standards an assay office can hallmark today.

What US law says the stamps must mean

In the United States there is no independent hallmarking office. Instead, the National Gold and Silver Stamping Act of 1906 makes it unlawful to ship gold or silver goods marked with a higher fineness than they actually have. For gold, the actual fineness may not be more than three parts per thousand below the mark, measured without solder, and the whole article including solder may be at most seven parts per thousand lower (three for watchcases and flatware); these figures date from the Gold Labeling Act of 1976, which took effect five years later. Since a 1961 amendment, a quality mark on a finished article must also be accompanied by the registered trademark or name of the responsible manufacturer or importer, applied the same way and close to the quality mark.

The FTC Jewelry Guides add rules for gold-covered goods. The key thresholds are:

• Gold filled (GF): a layer of gold alloy of at least 10 karat, bonded mechanically, making up at least 1/20 of the weight of all the metal in the piece. The karat of the layer must be shown, for example "1/20 12K GF".
• Rolled gold plate (RGP) or gold overlay: the same kind of bonded layer, but at least 1/40 of the metal weight, with the fraction and karat stated, for example "1/40 12K RGP".
• Gold electroplate (GEP): an electroplated layer of at least 10 karat gold with a minimum thickness equivalent to 0.175 microns of fine gold, about seven millionths of an inch.
• Heavy gold electroplate (HGE): the same, but at least 2.5 microns, about 100 millionths of an inch.
• Vermeil: sterling silver coated with gold of at least 10 karat and at least 2.5 microns thick.

Older pieces were made under earlier versions of these rules, and imported or homemade jewelry may not follow them at all, so a stamp is evidence, not proof.

British gold hallmarks

In the UK a gold item sold as gold must be hallmarked, unless it weighs less than the exemption weight, which is 1 gram for gold on the current dealer's notice. The hallmark has the same three compulsory parts as on silver: a sponsor's mark, a fineness number such as 375 or 750, and an assay office mark. Older British gold often shows a crown with the carat figure, such as 18 or 22, and a date letter. The Assay Office London notes that gold standards go back to 1300, when the "touch of Paris" (19.2 carats) was required, and that the standard was lowered to 18 carats in 1478. See British silver hallmarks for the assay office marks.

Marks that mislead

• "18KGP", "14KGE" or "HGE" describe plating. The karat number refers only to the thin surface layer.
• A karat stamp with no trademark on a modern US-market piece is a warning sign, because the law expects the two together.
• Numbers such as 750 on costume jewelry can be fake stamps. Look for wear at the edges and clasp, where a yellow surface may reveal a white or gray base metal.
• Old European pieces may have only small assay office symbols and no number at all, so a missing number does not mean the piece is not gold.

Safe checks you can do at home

Use a loupe to read the stamps on clasps, ring shanks and pin backs. Check worn areas for a color change. Try a magnet: a strong pull rules out solid gold. Avoid scratching or acid-testing antique jewelry, because the tests leave marks and only sample the surface. A jeweler with an X-ray fluorescence analyzer can measure the alloy without damage.

What drives value

For solid gold, the alloy and weight set a floor, but antique and designer jewelry is valued mostly on maker, period, design, gemstones, workmanship and condition. Gold-filled and plated pieces are valued as costume or period jewelry. To get a quick first opinion, scan the piece with Antique ID for an identification and an estimated value range. An estimate is not an appraisal: for anything that may be valuable, especially jewelry with stones, have it examined by a qualified jewelry appraiser or gemologist.

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