Lot 495. The Estate of Mary, Duchess of Roxburghe. Natural pearl and diamond double clip brooch, Cartier, circa 1935. Estimate 49,000 — 69,000 CHF. Lot sold 334,000 CHF. Photo Sotheby's

Composed of a pair of shield-shaped plaques of geometric design, set with circular-, single-cut and baguette diamonds, framing a central detachable motif accented with three brownish grey natural pearls, one button shaped, and two round to roundish, measuring approximately 10.05 x 10.10 x 9.90mm, 9.60 x 9.80mm and 9.65 x 10.25mm, and baguette diamonds, signed Cartier, two small synthetic rubies inset to the reverse to show how to orient the frame.

Accompanied by SSEF report no. 79530, stating that the three pearls were found to be natural, saltwater, with no indications of artificial colour modification. 

Sotheby's. Magnificent Jewels and Noble Jewels, Genève, 12 mai 2015, 10:30 AM