Base metal with a copper look to the metal on top. It is delicately indented and curved in a roughly rectangular shape. This pin has multiple manufacturing processes going on. It is an example of cloisonné, an enameling technique where a pattern is formed by wire soldered onto a ground plate, forming cells (cloisons) that are then filled with enamel. In this case, the ground plate is probably stamped out of a base metal with cells as part of the stamping. A design is already stamped into the bottom of ground plate (probably imitating guilloche). White translucent enamel covers the ground plate and fills in the cells. On the back is a round hinge and safety pin clasp. 1 3/16" long 3/16" wide