Vintage Art Deco Rhinestone 2 Piece Buckle

Vintage Art Deco Rhinestone 2 Piece Buckle Good used condition. The darker stones are present. It is likely the foil behind the stones got hot or wet over the years. There are no markings. It is not metallic. I tested it for silver content and I didn't recognize a reaction. However, I am very new to this aspect and barely recognized a reaction on my silver test piece.