This is a retro atomic era Japanese akoya saltwater cultured pearl cluster brooch with hand engraving. 

The pearls are 6.00-6.50mm round. They have fantastic luster with bright rosy pink overtones. 

It is made of solid sterling silver. It has an atomic burst design with hand engraving, delicate milgrain & braided silver. It is stamped "SILVER" which is an older mark for sterling. It measures 2 inches long. From Japan 1950's-1960's.  

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