Old jewelry will tell you what it is. You just have to turn it over.

Three questions account for almost every enquiry that reaches us: how old is it, what do the marks mean, and is it worth anything. In that order, because the last one depends on the first two.

• Eras How to Date Antique Jewelry: The Method Dealers Actually Use A step by step method for dating antique jewelry from its construction, findings, metal, stone cutting and motifs, with the date each piece of evidence actually proves.
• Hallmarks How to Read Hallmarks on Gold and Silver What each punch in a hallmark means, where to find the marks on a piece, how to read British, French, German, Scandinavian and Russian systems, and when a stamp guarantees nothing.
• Care & value What Is My Antique Jewelry Worth? The six things that decide the value of antique jewelry, the four different prices any piece has at once, and how to get a realistic figure before you sell anything.

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• Reference Hallmark decoder Type in what is struck on the metal - 585, 830S, an anchor, three towers - and read what it means, where it comes from and when it was used.
• Guided Date your piece Eight questions about the catch, the metal, the back of the setting and the cut of the stones. It returns an era, the reasoning and what it has ruled out.
• Visual Cut comparator Drag between an old mine cut and a modern brilliant and watch the table widen and the culet close. The difference is a century of technology.
• Arithmetic Gold calculator Weight and fineness in, pure metal and melt value out, with an honest note about why melt value is the floor and not the price.

Jewelry is made of fashion, technology and materials, and all three change at datable moments. These guides cover what each period made, what it made it from and how to recognise it.

• 1714 onward Georgian, 1714 to 1837 Closed backs, foiled stones, silver-topped gold and rose cuts. How to recognise genuine Georgian jewelry, why so little survives, and the one thing that will destroy it.
• 1837 onward Victorian, 1837 to 1901 The Victorian era lasted sixty four years and changed completely three times. How to tell Romantic from Grand from Aesthetic, and what each period used, made and left behind.
• 1890 onward Art Nouveau, 1890 to 1910 Plique-a-jour enamel, whiplash lines, insects and women. What Art Nouveau jewelry is, why so little survives, and how to separate period pieces from the endless reproductions.
• 1901 onward Edwardian, 1901 to 1915 What makes Edwardian jewelry recognisable, why platinum changed everything after 1900, how to read millegrain and pierced galleries, and how to tell period work from later copies.
• 1920 onward Art Deco, 1920 to 1935 What genuine Art Deco jewelry is made of, how calibre cutting and millegrain give it away, and the five checks that separate a 1925 piece from a 1975 or 2015 copy.
• 1935 onward Retro, 1935 to 1950 Why Retro jewelry is big, gold and sculptural, how platinum rationing and Hollywood shaped it, and how to tell period Retro from 1980s pieces that borrow the look.

• Hallmarks What 375, 585, 750 and 925 Mean on Jewelry Every fineness figure you will meet on gold, silver and platinum, what each one converts to in carats, which countries use it and what it tells you about age and origin.
• Stones & cuts Old Cut Diamonds: Mine, European, Transitional and Rose How to tell an old mine cut from an old European cut, a transitional and a modern brilliant, why the culet is open, and what each cut is worth against the others.
• Care & value You Have Inherited a Box of Jewelry. Now What? A practical order of operations for inherited jewelry: what to do first, what never to do, how to sort it, what to keep and how to decide what to sell.