From what era is this necklace?

by Lydia Simmons
(Lakewood, California)

My mother gave this to me in 2002. A neighbor that was 80 years old gave it to my mother in the 1960s before I was born in 1970. The necklace was in the neighbor's family as an heirloom. So we know that it is very old.

I have done some research and know that it is a thick Bizmark chain and some of the design on the pendant appears to be Greek Key.

Thank you for any help!