Vintage handmade sterling silver necklace, Southwestern / Western

Vintage handmade sterling silver necklace with large Seashell shaped pendant. Southwestern/ Western style. With natural mother of pearl inlay. Also with some kind of green stone on top. The chain is stamped CORO and STER on the plate and Sterling on the clasp. The pendant is not stamped, but it's outer layer was acid tested as 925 sterling silver. The inner filling looks like clay (as a base for the stone inlay, shown in one of the closeup pictures). The chain was possibly rhodium plated, with some plating wearing off, but is still in good overall condition. 15" chain. 1.75" pendant (with bail).