What metal has the U.S. nickel coin primarily been made of since 1866?

The US 5 cent coin, commonly called a nickel, contains mostly copper.

Nickels are made from a metal alloy called cupronickel, which is also known as "White copper" and "Nickel Silver". The cupronickel alloy in the nickel coin is 75% copper and 25% nickel.

The nickel coin alloy was changed during World War II when nickel was needed for the war effort. The new alloy made from copper (56%), Silver (35%) and Manganese (9%) was used until the end of the war, at which point the mint reverted to using the standard cupronickel alloy from before the war.

Several other countries coins also use this formula - including the Swiss franc, and the South Korean 100 and 500 won coins.

Other items made from cupronickel include flutes, trumpets, and other musical instruments.