platinum ring with emerald and diamond

A platinum ring featuring a large sugarloaf cabochon-cut emerald (app. 12 ct, 15.7 x 11.5 x 9.5 mm, moderate oil, possibly Russian, NEL certificate E2620920). The rich, velvety emerald is flanked by 20 brilliant-cut diamonds (10 on each shoulder), circa 1960.

weight: 9.9 g
ring size: 16.75 mm / 6 1/4 US / 53