The Atlas · Gold fineness mark
750 means 18 karat gold: 750 parts gold in every thousand, 75% gold by weight. It is the standard of most fine European jewellery, and it is the highest fineness that turns up routinely in an American estate box.
What does 750 mean on jewelry? — answered here in full, free, with nothing asked of you.
Three quarters gold is the fineness at which houses work when they intend a piece to be permanent: it is soft enough to be raised and chased, rich enough in colour to need no plating, and expensive enough that a maker who used it rarely cut corners on the rest of the piece. A 750 mark is therefore weak evidence about value on its own and strong evidence about intent — it tells you a maker thought this piece worth good metal, which is a reason to look harder at the stones and the workmanship.
French 750 is worth singling out. Since 1838 French 18 karat has been struck with an eagle's head in a lozenge rather than a number, so a French piece may carry no 750 at all; a rhinoceros head, a scallop shell or an owl marks imported gold instead. Italian 750 usually sits beside a star, a number and a two-letter province code identifying the workshop, which can often be traced to a named firm. British 750 appears with a crown and the numerals 18 before 1975 and as 750 in an oval after it, always with a town mark and a date letter.
The trap on 750 is the French words. Plaqué or, doublé or and similar phrasings mean a gold layer over base metal, and they sometimes appear stamped near a fineness number describing only that layer. Any wording alongside the number, in any language, needs reading before the number is believed.
The stamp is present and legible: this metal is declared 18 karat gold, 750 parts per thousand.
European manufacture in a workshop that chose good metal. An eagle's head points to France, a star with a province code to Italy, a crown and town mark to Britain — each of which narrows the maker and often the decade.
Whether the stones in it are natural, synthetic or glass; the carat weight of anything set; and the piece's own weight. On 18 karat pieces those unknowns are usually worth more than the gold, which is exactly why the photograph is not the end of the job.
Next step
Photograph any punch that is a picture rather than a number — an animal head, a star, a shaped shield — as close as the phone will focus. Those are the marks that name a country and sometimes a workshop, and they carry more value than the 750 does.
14 karat. About 22% less gold per gram, and a different market: workaday rather than fine.
Silver fineness, not gold. A high number on a white metal piece is far more often continental silver than anything gold.
Gold electroplate over base metal. The fineness describes a coating microns thick.
French for gold plated and gold doubled. Both are a skin, not solid metal, whatever number sits beside them.
Free, and nothing asked of you
One mark answers one question. A box answers the real one — which pieces deserve money and expertise, and which nine are costume. Email the photographs to the house inbox: the whole box laid out, then any stamps you can find. We read them and reply by hand.