Art Nouveau emerald and diamond ring

Rare 18 carat yellow gold French Art Nouveau ring set with an Emerald of approximately 0.50 ct and 12 rose cut diamonds.
The current ring size is 17,8 mm Ring size: 55,3 mm (circumference), 17¾ mm (cross section),  US size 7½, UK size P.
French Hallmarks for 18 carat gold and a makers mark With the letters G+V in a diamond shape.