Vintage 1.00 Carat European Diamond Engagement Ring PlatinumVintage 1. 00 Carat European Diamond Engagement Ring Platinum. This Mid Century engagement ring features a beautiful 1. 00 carat Old European cut diamond set in platinum. The primary stone is set with four prongs that are rather wide and flat, creating an almost square shape from a top down view. On the shoulders are neat sections outlined in milgrain detail holding accent diamonds.