Copper
Coinage metal of the copper piece, which is round and the same size as the silver piece and is told from it by color and weight.
Sources
Copper can be easily isolated by relatively primitive metallurgical processes. It is sourced from all of the mundane copper ores, and as hydrothermal native copper.
Minting
Because copper is so easily isolated, copper minting is not a prestige process, and can be undertaken by even a relatively small foundry in a town. People do not tend to worry much about the weight of metal in coinage: a rough disk of about the right size and thickness is usually adequate.
See also: Coinage, Dwarven Minting, Bronze, Brass