Value of single strand Mikimoto grey (black?) necklace/earring set from Japan

by Randi Dubey
(California)

This set was purchased in the mid-late 1950''s or early 1960's. It is in an original box. My uncle used to lecture there and purchased it for my grandmother. I am curious of the authenticity, value and any other information you may have.

I believe the clasp is silver. Is that common with these pearls. I am not sure what metal the earrings are made of?
Photo included: