Platinum Plated Antique Victorian Brooch Pin Brown Agate Closed Back

Stunning piece, I think the stone it's agate. The material is white metal platinum plated. It is silver but not hallmarked hence we sell it as white metal. The condition is good, the pin is safe, the stone has some minor imperfections on the corner please see photos. Nothing major, could be just from the natural stone. Measures approx 4x1.6cm. Closed back. Thanks for looking:-)