Lady's emerald and diamond wristwatch, Cartier, circa 1920. Photo Sotheby's

The circular dial applied with Roman numerals and a cabochon emerald crystal, the bezel millegrain-set with circular-cut diamonds, the bracelet set with circular- and single-cut stones, bracelet expandable, dial signed Cartier, case indistinctly numbered, French assay marks. Estimate 19,000 — 27,000 CHF. Lot sold. 37,500 CHF (31,142 EUR) 

The emerald crystal is a later addition, not recorded in Cartier's archives.

Sotheby's. Magnificent Jewels and Noble Jewels. Geneva | 14 May 2012 www.sotheby's.com