Reserved - C -Art Deco 1920s 18ct Gold Platinum Diamond 0.45ct Geometric Gemstone Engagement RingArt Deco 1920s 18ct yellow gold and platinum ring. The ring features 0. 45ct of diamonds set into a square setting of 10 diamonds. Art Deco jewellery typically has strong geometric lines as shown in this ring. This is a real statement ring, the diamonds have beautiful shine and impact. The ring has a number of hallmarks indicating it was made by 'HS' from 18ct yellow gold and platinum. ERA Art Deco, 1920 1930. HALLMARKS HS, 18ct, PLAT English.