There's around £60 million-worth of vintage jewellery lying around in British people's homes without them knowing it, according to auction house Bonhams.

It could have been handed down from previous generations, one of your signature party pieces or even in your child’s dressing up box, Bonhams says.

Jewellery prices have been rising in recent years as investors move away from stocks and shares into more tangible commodities like diamonds, gemstones and collectable pieces.

And it cites the example of a dusty ruby brooch, which was bought in a Cambridgeshire charity shop for £1.50 and sold for £2,400 at auction after ‘scratches’ on its back were identified as a Cartier signature. That's a whopping 1,600 times its purchase price.

Remarkable finds

Some great success stories have come out of valuations.

One lady brought in a 4.50 carat single-stone ruby ring which had been passed on by her grandmother. After being sent away for testing, Bonhams discovered that it was an ultra-rare Burmese unheated stone, which sold for £134,500.

Another found a five carats brilliant cut diamond in an early 20th century ring mount, which his mother had buried in the garden in a jar and didn’t tell him where it was before she died. It was worth the year of digging around the garden to find it as it was eventually sold for £20,000.

And one man from East Anglia brought in a bright green bangle for valuation. It was identified as jade and was worth an estimated £20,000-£30,000.

Bonhams went on to sell it in Hong Kong for a massive £443,500.

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Identifying valuable jewellery 

Emily Barber from Bonhams has given us some advice on how to identify high-value items of jewellery.

Gather information

Try to gather as much information as possible as to where the piece came from. Look for original receipts, fitted cases, letters or notes giving an idea of where it was purchased, when and by whom. 

Look out for the big jewellery houses such as Cartier, Van Cleef & Arpels and Tiffany's. Jewellery made by these brands in the first half of the 20th century are highly sought after.

Look for marks

Check the jewellery to see if it has any marks. Is it signed?

Does it have UK hallmarks – stamps that when read together tell you the city, date, precious metal content of the piece?  Perhaps it has other marks like letters or stamps.

These could be maker’s marks or foreign assay marks. For example, an eagle’s head stamp indicates French manufacture in gold and a dog’s head indicates French manufacture platinum. 

French marks are a sign that the piece is good quality as some of the best period jewellery was made in France.

Pearls

As for pearls, there is a huge difference in value between cultured pearls – formed by man’s intervention by ‘farming’ the oyster – and natural pearls, which are solid pearls formed over many years naturally. The only way to be absolutely certain is to x-ray the pearls, but a jewellery specialist will have a good idea by looking at the pearls’ shape and lustre. 

The difference in value is huge.  A cultured pearl necklace is worth a few hundred pounds at auction; its natural counterpart comes in at several thousand pounds.

Know your gems

Check out colourless gems. Modern diamond cuts are very precise but older cuts are lumpier and less precise.

There has been a huge increase in the value of coloured gems (rubies, sapphires and emeralds). Look for strong, bright colours and good transparency. 

Antique gems tend to be untreated (modern gems are often heated to ‘improve’ them) which makes them more valuable and antique gems tend to come from premier mines which are now exhausted. They are rare and demand is huge.

Don't just rely on your judgment

Just because a jewel may not be to your taste does not mean it is not valuable. Jewellery goes through fads and fashions at auction and something that was out of fashion a few years ago might now be on the up.  For example, jewellery made in the 1970s and 1980s is now collected widely.

Is it unusual?

If a jewel looks highly unusual it might well be a unique, one of a kind piece and therefore carries a premium. It could be by an artist jeweller, a craftsman who did not work for a big jewellery organisation.

Look at the workmanship

The very best jewellery has been crafted to an excellent finish on all sides of the piece, not just the front part which people see. Look at the back and underneath too. 

Going for a valuation

Bonhams is holding free valuation days as part of its ‘Jewellery in June’ campaign. You can visit its regional offices in the North East, Yorkshire, Humberside, Nottinghamshire, Lincolnshire and North Derbyshire but by appointment only.

Goldsmiths also offers valuations. There's a £60 flat fee for the first item and £45 for each additional item.

For local services, go to the Institute of Registered Valuers. It lists valuers across the UK.

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