Three diamond or gemset rings testing for 18ct gold

the first a three stone diamond ring with graduated round brilliants, claw set, plain tapered shank size N, stamped '18ct & Pt', and engraved with initials and the date 25.12.32, total estimated weight of diamonds approximately half a carat; also a 19th century diamond ring with three old cushion cut diamonds, the central one in a diaper recess within a square motif, each shoulder similarly set with a smaller diamond, tapered shank size L½, stamped '18', total estimated diamond weight approximately 0.25cts; and an 18ct gold signet ring set with an oval lapis lazuli, partial hallmarks, ring size L (Qty: 3)