Gunmetal
Gunmetal is a kind of bronze, an alloy of copper, tin, and some zinc, originally used chiefly for making guns, but later superseded by steel. It is also called red brass in America.
Gunmetals produced for different purposes vary slightly in composition. In some cases, the alloy may be composed only from copper and tin, or from copper, tin, and lead. It has many uses in industry, and is used for statues and various small objects, e.g. buttons.
U.S. Government bronze spec. G is a gunmetal composed of 88% copper, 10% tin, and 2% zinc. U.S. Government bronze spec. H is composed of 83% copper, 14% tin, 3% zinc, and 0.8% phosphorus.
Gunmetal can also mean steel treated to simulate gunmetal bronze. Bushes made of this metal are used in machinery
Gunmetal is also a name for a shade of matte gray/silver, aka machine finish.
Other Uses?
The famous British Victoria Cross captured at the Siege of Sevastopol (1854-1855) is supposedly made of Gunmetal.