A RUSSIAN EARLY 20TH CENTURY SAPPHIRE AND DIAMOND RING CIRCA 1910The Art Nouveau style panel with a vertical row of two old cut diamonds and a central squared cushion cut sapphire, in claw settings, to scrolled crossover shoulders set with old European cut diamonds, approximately 1 carat total, the shank stamped with 56 Zolotnik mark and St Petersburg mark, and two further unidentified marks Size/dimensions: finger size M 1/2Gross weight: 4.2 grams