Vintage Southwestern sterling silver belt buckle with stamped rolled edge. It is set with a large very fine spider web turquoise that has large quartz inclusions. This stone has the attributes of the #8 Mine. This mine was located in Nevada just north of the Carlin Mine. I am not 100% positive on this ID, but it is likely. In any case, it is a very fine natural American turquoise stone. 🇺🇸 This stone measures 2 3/8" by 1 1/2". 

It is also set with three natural red branch coral stones. 

The buckle measures 3 1/8" by 2 1/2". For a belt that is 1 3/8" wide. Weight: 84.6 grams. Hallmarked KB on the back. I do not know whose mark this is.