Buying second-hand and vintage jewellery has become popular in recent years. Pieces made more than 100 years ago are generally regarded as antiques, whereas those from 30 years or more are considered vintage. 'It's hard to define estate jewellery because if someone buys a diamond today and passes it on tomorrow, that diamond belongs to his estate and can be considered estate jewellery,' says David Warren, senior international specialist at Christie's. That said, most experts associate estate jewellery with pieces that are previously owned and more than 30 years old. 'It's very fashionable and timeless to buy estate pieces,' says Catherine Cariou, patrimony specialist at Van Cleef & Arpels. 'There are many customers who want vintage pieces from the 1920s till the 1970s.' Part of Cariou's role is to shop for vintage pieces made by Van Cleef & Arpels. She buys from auctions, private dealers and individuals. 'In Paris, there's a hippie revival going on. Collectors are looking for pieces made in the 1970s, and long necklaces are popular.' Signed jewellery is always more valuable. 'Anything by one of the top brands, often French houses such as Cartier, Boucheron and Van Cleef & Arpels from the 1920s, is always sought after,' says Warren. As are stones from old mines. 'People are keen to look for stones from old mines, such as the fine old Burmese rubies, which are almost impossible to find today.' Besides the value of the stones, there's also the question of provenance. If the previous owner is someone famous, the pieces are likely to command higher prices. Vicki Sek, director of the jewellery and jadeite department at Christie's Asia, says Hong Kong buyers are savvy when it comes to investing in estate jewellery. 'Hong Kong buyers pay more attention to the rarity of the stones and quality of the piece, rather than whether the piece is previously owned by a famous person,' says Sek. When buying estate pieces, buy from reputable auction houses and dealers specialising in estate jewellery. Warren suggests using a jeweller's magnifier to examine the gemstones - for damage, missing stones, the quality of setting and mounting. Avoid pieces that have been significantly altered. 'Examine it and research to see if the piece has any stones that have been replaced,' says Cariou. 'For example, if the emerald has been replaced by a ruby or if the gold setting has been changed to another material.' If you have an inherited a piece you don't like, bring it to a specialist for evaluation. 'Don't reset the stones as it may depreciate its value,' says Cariou. Warren says part of the charm of vintage pieces is their worn-in quality. 'People who buy antique or vintage jewellery like the darkening of metal. Clean the stones, but not the metal.' Shopping list Christie's 22/F Alexandra House, 18 Chater Road, Central; tel: 2521 5396 (christies.com) Sotheby's Suites 3101-3106, One Pacific Place, 88 Queensway, Admiralty; tel: 2822 8119 (sothebys.com) Van Cleef & Arpels Shop G15, Prince's Building, Central; tel: 2522 9677. Popular estate items include long necklaces and watches with secret compartments.