.55 Vintage Halo Diamond Engagement Ring in 18k White Gold. 55 Vintage Halo Diamond Engagement Ring in 18k White Gold. This Mid Century engagement ring features a . 55 carat Round Brilliant cut diamond and a halo of accent diamonds in 18k white gold. The bezel set center stone is eye clean and high in brilliance. The Mid Century artistry is found in the halo of twenty two (22) accent diamonds, each weighing . 005 carats. The setting of the halo features four triangle designs that look both vintage and