a nickel made of

[SanLevi]

While the provided context links to relevant sources, the text itself does not contain the specific information needed to answer the question. Based on established numismatic and historical knowledge, the composition of the United States five-cent piece, commonly called a nickel, has a specific and consistent alloy for most of its history.

The standard metallic composition of a U.S. nickel is a cupronickel alloy. This alloy consists of 75% copper and 25% nickel. Despite its name and silvery appearance, the coin is predominantly made of copper. This composition has been used for the five-cent piece since its introduction in 1866, with one notable exception during World War II.

During the war, nickel became a critical strategic material for the production of armor and other military necessities. To conserve this metal for the war effort, the U.S. Mint altered the coin's composition for a limited period. From mid-1942 through the end of 1945, these "war nickels" were struck from an alloy of 56% copper, 35% silver, and 9% manganese. These coins are identifiable by the large mint mark (P, D, or S) placed on the reverse above the dome of Monticello. Following the war, the mint reverted to the original 75% copper and 25% nickel alloy in 1946, and that composition remains the standard for the coin today.