This is a very old piece, a vintage 1920s or 1930s plastic brooch in the shape of a fancy buckle. Made in two layers: the bottom layer is a dark green swirled plastic, while the upper layer is a carved gold glitter plastic, adorned with small clear rhinestones. The brooch components are clearly cut-outs; they are not molded. The glittery-gold decoration has been scored and inset with rhinestones. The plastic may be galalith, though I could not get a sour-milk smell out of it.
The pinback is mounted on two small plastic discs, and glued on to the back of the brooch. Simple "C" clasp. In excellent condition, except that it looks like someone once tried to test it for Bakelite by hot-pinning it. (It failed the test.) Unsigned. Measures 3" high and 1-7/8" across.