Platinum and Diamond Ring, Harry Winston. photo Sotheby's

The emerald-cut diamond weighing 15.98 carats, flanked by tapered baguette diamonds, size 6½, signed Winston, maker's mark. Estimate 300,000—400,000 USD. Lot Sold 662,500 USD

Accompanied by GIA report no. 2125769536 stating that the diamond is I color, VS1 clarity.

Sotheby's. Important Jewels, 02 Feb 11, New York www.sothebys.com