Sterling Silver Amethyst Slider Pendant - Modernist Design

With only a makers initial of M to the back of the piece, I am thinking that this C.19780/1990 jewelry piece is Native American made but I could be wrong. In a modernist design, this Sterling Silver (hallmarked as pictured) pendant is a stylized horseshoe design set with a very large polished cab of amethyst. Height is 1-7/8"; width is the same. Weight is a respectable 15.9 grams. Condition is very fine with a high shine to the silver and no roughness to the stone top. A pair of large rings are at the back making this piece a slider which can be placed on a strand of beads, cord, ribbon, thin chain or large. A stunning design that is most pleasing!