1940's Round Brilliant Cut Diamond Engagement Ring1940s Round Brilliant Cut Diamond Engagement Ring. This Retro engagement ring features a . 19 carat round brilliant cut diamond set in 14 karat white gold with a 14 karat yellow gold shank. The primary stone is set with four fishtail prongs seated above shoulders that hold smaller accent diamonds. The two toned look allows for nice color dimension that goes beautifully with the stepped up vintage design.