A historic pearl and diamond necklace worn by a Swedish Queen will be going up for auction in Hong Kong on 12 October. This 19th-century necklace, formally known as the Leuchtenberg Necklace, is thought to be made by jeweller Marie-Étienne Nitot, the founder of the House of Chaumet. Sotheby’s describes the necklace as “composed of two strands of natural pearls measuring from…