Platinum, conch pearl and diamond necklace. Photo Sotheby's

Designed as a graduated double-strand composed of 135 conch pearls measuring approximately 11.6 to 4.3 mm., spaced by diamond beads measuring approximately 3.8 to 2.5 mm., completed by a modified hexagonal-shaped clasp set with hexagonal-shaped, baguette and old European-cut diamonds weighing approximately 1.60 carats, length 25½ inches, clasp signed Cartier Ltd., London. Estimate 450,000-650,000 USD. Lot Sold: 1,118,500 USD

Sotheby's. Magnificent Jewels. New York | 07 Dec 2011 www.sothebys.com