On 1 July Sotheby's in London will offer an amber heart-shaped pendant with a carved portrait of Elizabeth I

The appraisers expect £100,000 to £150,000. Yet last November an anonymous collector bought this pendant at auction in Edinburgh for £5,588, as a mere old article of amber. After careful attribution, the inconspicuous trinket was recognised as a Renaissance jewel bearing a portrait of Elizabeth, which added some 1,800% to the price.

The pendant is attributed to the celebrated Königsberg amber masters Hans Klingenberg or Georg Schreiber, who worked for the ducal court of Prussia. The portrait is carved after an engraving of 1592 by Crispijn de Passe the Elder, itself derived from a drawing by the English miniaturist Isaac Oliver. On the reverse is a parrot, the Renaissance symbol of the Virgin Mary.