Vintage Three Stone Diamond Ring The Vintage Jeweller Vintage Diamond Three Stone Gold Ring at 1stDibs 0.75 Carat Vintage 3 Stone Diamond Ring Set in 14 Karat White Gold at Vintage Diamond, Platinum and 18 Carat Gold Three Stone Ring For Sale. A vintage trilogy ring. Set with three old brilliant cut white diamonds, centre 3mm and each side a 2. 4mm diamond. Total estimated at 0. 20 carats, colour H j, clarity Si All diamonds set in to a platinum head , 11x4mm , square design, early 20th century. Weight 2. 2grams. Stamped 18CT PT, tests as 18 carat gold, platinum shoulders, no hallmarks required for this period Size K, we can resize free of charge.