Koller Auktionen

Koller is Zurich's main auction house and holds four jewellery sales a year, drawn mostly from private collections and spanning all periods. Lots regularly include signed pieces from Boucheron, Bulgari, Cartier, Harry Winston, Van Cleef & Arpels and others, so vintage rings turn up across a wide price range. Specialists value items free of charge, so it's a useful route for buyers and sellers alike.