This is a vintage bright blue Japanese akoya saltwater cultured pearl necklace.

The pearls are 6.25-6.50mm and are round with great luster and light rosy overtones. They are a medium blue/gray color. They appear more blue or gray in different lighting. Some color variation between pearls. Moderate amount of natural blemishes. 

Clasp is white gold filigree with a single 1.50mm diamond on the top. It is stamped "14K" for solid gold. Total length is 17.50 inches. From mid-century Japan. 

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