Vintage Three Stone Diamond Ring For Sale at 1stDibs A vintage three stone diamond ring Vintage Three Stone Diamond Ring Platinum 2 Carat For Sale at 1stDibs Antique Three Stone Diamond Ring For Sale at 1stDibs. 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.