.50 Old European Cut Round Halo Engagement Ring in Platinum. 50 Old European Cut Round Halo Engagement Ring in Platinum. This Modern era engagement ring features a . 50 carat Old European cut diamond and a halo of accent diamonds in platinum. The bezel set center stone is eye clean and glitters when touched with light. A halo of twelve (12) accent diamonds, each weighing . 03 carats, circles the center diamond. Two (2) . 01 carat diamonds decorate the shoulders of the band. From the profile, a vintage