Speculum metal metal mixtures usually contain two parts copper to one part tin along with a small amount of arsenic, although there are other mixtures containing silver, lead, or zinc. The knowledge of making very hard white high luster metal out of bronze-type high-tin alloys may date back more than 2000 years in China although it could also be an invention of western civilizations. Such metals were used in sculpture and to make more effective mirrors than the more common yellow easily tarnishing bronze mirrors. In that era mirrors of speculum metal, or any precious metal, were rare and only owned by
Ampco Metal into the production of aluminium bronze alloys as sand castings, forgings and centrifugal castings. The company was renamed "AMPCO METAL" in 1930, by which time it had built itself a reputation as a reliable producer of high quality alloys. The Second World War strongly increased the demand for copper-based alloys and industrial bronzes, especially in the field of aeronautics. By 1944, manufacturing operations had grown from 100 to 2,500 employees, and every American airplane carried AMPCO METAL parts somewhere in its structure—in its engines, landing gear, propellers or airframe. In the marine environment, AMPCO METAL propellers were manufactured for landing