Vintage Brutalist-style Unusual Goldtone Brooch

This unmarked brooch is quite unusual. The rough texture of the main goldtome metal is sort of like a sponge. The middle goldtone ring has a roughened texture, as well as smooth, raised streaks. The construction is also unusual as you can see by the photos of the back side. The pin is slightly bent, but works well in the rollover clasp. Otherwise no flaws. Measures 2.25 x 1.75 inches.