Jewelry Stamps Decoded: What L, GF, 325, 333 and 520 Mean

Cuff & Steel

316L steel - $49

Vintage

316L cuff - $39

Anchor Chain

316L and cord - $69

Jewelry stamps fall into three groups: purity marks such as 925, 585 and 750 that state a precious metal fraction; material marks such as 316L that name an alloy specification; and coded or decorative marks that make no claim at all. A single letter L is not a purity mark - it is most often a maker's initial, the surviving character from a worn 316L stamp, or a size indicator. GF means gold-filled, 333 means 8-karat gold, 325 is not a standard mark, and 520 is a Chinese love code rather than a metal claim.

Almost every guide to jewelry stamps lists the same six marks and stops. The stamps people actually find on things they own - a lone letter, an unfamiliar three-digit number, an abbreviation that turns out to be a manufacturing term - are the ones nobody covers.

This is the complete reference. Every mark you are likely to encounter, what it claims, what it does not claim, and which of them are worth nothing at all.

The Quick Answer

L: The Stamp Nobody Explains

A single L is the most searched and least documented mark in jewelry, and the reason is that it has no single meaning. It is not a purity mark in any national system.

Four explanations account for nearly every case, and you can usually tell them apart in under a minute.

1. A maker's or designer's initialBy far the most common. Manufacturers and designers stamp initials, and a solitary letter with no number beside it is usually one of those. If the L sits alone, is stylised, or appears alongside a symbol or logo, this is almost certainly it.
2. The survivor of a worn 316LSteel jewelry is frequently stamped 316L on a clasp or an inner surface. The numbers are shallow and rub against skin all day, and the L often outlives them. Check whether the piece behaves like steel - very weak magnetic response, no tarnish, no green marks - and look for faint traces before the L under magnification.
3. A size indicatorOn adjustable pieces, bangles and some cuffs, L simply means large - part of an S, M, L run rather than any material claim. If the piece comes in sizes and the letter is on a tag or an end cap rather than struck into the metal, this is the likely answer.
4. Part of a longer codeKL, GL, PL, SL and similar combinations appear as manufacturer or line codes, and a partially worn stamp can leave only the L visible. Look at the spacing: a lone letter centred in a clear field is a mark; a letter crowded at the edge of a worn area is a fragment.

Miami Cuban - Where a Steel Stamp Lives

316L link bracelet with a fold-over clasp, $49.

On a link bracelet the mark almost always sits on the clasp, which is the single most rubbed surface on the whole piece - which is exactly why worn 316L stamps are so often reduced to a lone L. Ours are 316L in the links, the pins and the fold-over clasp, and we state the grade in the listing rather than relying on a stamp that daily wear will eventually thin. The gold-tone version is PVD on the same alloy, so it carries no plating mark because there is no plating.

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GF, GP, HGE and Vermeil: The Coating Marks

This family causes more confused purchases than any other, because all four involve real gold applied to something else - in wildly different quantities.

The row that surprises people is the last one. PVD contains no gold and outlasts every genuine gold plating on the list, because it is a hard vacuum-bonded coating measured in microns rather than a chemical deposit measured in fractions of one. If you want the colour rather than the metal, PVD is the durable answer and the honest listing says so.

Gold-filled and gold-plated differ by roughly two orders of magnitude in the amount of gold present. They differ by two letters on the stamp.

Arc - Coated, and Saying So

One-piece forged 316L cuff, $49, bare and PVD gold-tone.

Arc Golden is the PVD row of that table in a real object. It contains no gold, it is not stamped as though it did, and we describe it as gold-tone rather than as gold-anything - which is the distinction the GP and HGE marks exist to blur. The trade is stated openly: no gold value, no resale, and a colour layer that survives sweat, chlorine and years of daily wear because it is bonded rather than deposited. Arc Steel beside it is the same forging with nothing on it at all.

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333 and the European Karat Ladder

Three-digit gold marks state parts per thousand, which makes them convertible to karats with one division.

The practical consequence is jurisdictional rather than metallurgical. A piece stamped 333 is genuinely 8-karat gold and can be sold as gold in Germany; the same piece cannot legally be described as gold in the United States, where the floor is 10 karat. Neither country is wrong - they simply drew the line in different places.

It also explains a common confusion with inherited jewelry. European pieces brought to a US buyer are frequently valued lower than expected not because they are fake but because they fall below the local threshold, which affects both marketability and resale.

325: Not a Standard

325 appears on jewelry regularly and corresponds to no purity standard in any major national system. There is no 325 fineness for gold, silver, platinum or palladium.

Three explanations cover almost every case. It is a maker's model or reference code, since manufacturers routinely stamp internal numbers. It is a worn or misstruck 333, where the middle character has been damaged - and this is common enough that a 325 on an otherwise European-looking piece is worth a second look under magnification. Or it is decorative, with no claim intended.

What it is not is a purity guarantee. If a seller presents 325 as a fineness mark, that is a signal to ask what the metal actually is - and to weigh and test the piece rather than accept the number.

Vintage - Bare Alloy, Nothing to Misread

Open-back 316L steel cuffs, $39.

There is a reason steel jewelry generates fewer stamp questions than precious metal. A grade like 316L names a composition that is either used or not, with no fraction to shade and almost no incentive to counterfeit, because the alloy costs too little for faking it to save anything. On an open cuff with no clasp there is also nowhere for a mark to hide and nothing that will rub it away. At $39 the specification is the whole claim.

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520: The Love Code

520 on a chain or a bracelet is not a metal mark at all, and the explanation is linguistic.

In Mandarin, the digits five two zero read aloud sound close to the phrase meaning I love you. The resemblance turned 520 into shorthand across Chinese internet culture, and 20 May - written 5/20 - became an informal romantic holiday on which gifts, and gift jewelry, are exchanged.

So a 520 stamp is a message to a recipient rather than a claim about composition. The related code 1314 works the same way, standing in for a phrase meaning a lifetime, and the two are often combined to mean loving you for a lifetime.

Practically: a piece stamped 520 might be anything. The number tells you what it was given for, not what it is made of, and the material still needs establishing separately.

The Complete Stamp Reference

Everything above plus everything else you are likely to encounter, in one table.

Eros - Two Materials, One Specification

316L cuff with cotton or leather centre, $59.

Mixed-material pieces are where stamp reading gets genuinely hard, because the metal you can inspect may not be the only metal present. Frames, internal pins and hidden connectors are rarely marked and frequently a different alloy from the visible part. On Eros the frame and every metal component are the same 316L, which is a specification decision rather than a stamping one - and it is the reason we publish the grade in the listing rather than expecting anyone to find a mark on a cuff this size.

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Marks That Mean Nothing

The 18KGP entry deserves particular attention, because it is the single most effective piece of stamp ambiguity in the market. At a glance it reads as 18-karat. The two letters that change everything are appended at the end, in the same size, where a hurried buyer will not weigh them.

Anchor Chain - Where Unmarked Metal Hides

316L box links with marine cord, $69, six colourways.

A hybrid build has four separate metal parts - machined links, a fold-over clasp, connector pins and internal joints - and on most such bracelets only one of them is ever marked. That gap is where a cheaper alloy is easiest to place and hardest to detect, because a stamp on the clasp says nothing about the pins. Ours are 316L throughout, which is a claim about the parts nobody can inspect rather than about the one that carries the stamp.

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How to Read Any Stamp

Five questions, in order, that resolve almost any mark you find.

1. Is it a number or a letter? Numbers in the 300 to 999 range are almost always purity in parts per thousand. Letters are makers, materials, sizes or methods.

2. Is there a suffix? GF, GP, GEP, HGE, RGP and P after a karat figure change the meaning completely. Read to the end of the mark before concluding anything.

3. Does the number map to a known fineness? 999, 958, 925, 916, 900, 800, 750, 585, 417, 375, 333 are real. Anything else - 325 included - is not a standard purity mark.

4. Is the strike crisp or soft? Genuine marks on solid metal are struck under pressure and have sharp vertical edges. Cast-in counterfeits look rounded or slightly blurred under magnification.

5. Does the metal behave the way the stamp claims? This is the one that settles it. Weight against size, magnetic response, tarnish over months and skin reaction all test the claim rather than the mark. A stamp is evidence; behaviour is proof.

The Bottom Line

Jewelry stamps do three jobs: state precious metal purity as parts per thousand, name an alloy specification, or describe a coating method. Everything else is a maker's mark, a size, a message or marketing.

A lone L is not a purity mark - it is a maker's initial, a worn 316L, a size, or a fragment. GF is gold-filled and vastly more substantial than GP. 333 is genuine 8-karat gold that falls below the US threshold. 325 corresponds to no standard at all. And 520 is a love code that says nothing about metal.

The habit worth keeping is simple: read to the end of the mark, check the number against the real fineness list, and then test whether the metal behaves as claimed. A stamp is a claim made by whoever struck it, and the object itself is the only witness that cannot be edited.