A rare antique diamond necklace, worn at two British coronations and possibly linked to Marie Antoinette, is expected to sell for more than £1 million at auction. The 18th century necklace, featuring approximately 300 carats of diamonds, was part of the Marquess of Anglesey family collection for around 100 years before being sold in the 1960s. It is estimated to sell for £1,348,416 to £2,097,536 in the Sotheby's Geneva sale in November. The necklace, composed of 500 diamonds, will embark on a global exhibition tour before the auction.