Bronze is an alloy of copper and tin, though other elements such as zinc or lead are sometimes added. It is typically brown to reddish-brown, harder and more wear-resistant than pure copper, and develops a stable patina over time, which helps protect the surface. Bronze has been used for coinage since antiquity and was especially common for low-denomination coins in many monetary systems. In the first half of the 20th century, it was progressively replaced by cheaper or more readily available alloys.
