This is a vintage retro Japanese akoya saltwater cultured pearl and 14K yellow gold tie tac by Anson.

The pearl measures 6.50mm. It has great luster with bright pink overtones.

It is set into a solid gold prong setting that is stamped "14K" "ANSON". The back of the tie tac and button loop is not gold as is common. It comes in the original green velvet box from the 1950's. 

All pearls are truly vintage and have only been lightly cleaned.