Composition of US coins

When the U. S. Mint was established in 1792, the law required that all coins be made of gold, silver or copper. For a considerable period of time afterwards, gold was used in the $10, $5 and $2.50 pieces, silver was used to make the dollar, half-dollar, quarter, dime and half-dime while the penny and half-cent coins were made of copper. In 1933, during the Great Depression, the U.S. Mint stopped making gold coins altogether. In 1965, as a result of a severe silver shortage, Congress dictated that silver no longer be used in making quarters and dimes. In addition, the silver content of the half-dollar (previously 90%) was reduced to 40% in 1965 and then eliminated entirely in 1971. All of these coin denominations are now composed of copper-nickel clad with an outer layer of a 75% copper, 25% nickel alloy and a pure copper core. Nickels are made of the same copper-nickel alloy but without the copper core.

• From 1793 to 1837, the cent was made of pure copper
• From 1837 to 1857, the cent was made of bronze (95% copper, and 5% tin and zinc)
• From 1857, the cent was 88% copper and 12% nickel, giving the coin a whitish appearance
• From 1864 to 1962, the cent was again bronze (95% copper, and 5% tin and zinc) -- [1]
• From 1962 to 1982, the cent's tin content, which was quite small, was removed. That made the metal composition of the cent 95% copper and 5% zinc
• From 1982, the composition was changed to 97.5% zinc and 2.5% copper (copper-plated zinc). This was done as a cost cutting measure and to make the penny lighter in weight

[1] -- In 1943, the coin's composition was changed to zinc-coated steel. This change was only for the year 1943 and was due to the critical use of copper for the war effort. However, a limited number of copper pennies were minted that year, makeing them a rare, collectible item.

Reeding on US Coins

The dollar, half-dollar, quarter, and ten-cent coin denominations were originally produced from precious metals (gold and silver). Reeded edges were eventually incorporated into the design of these denominations to deter counterfeiting and the fraudulent use of the coins, such as filing down the edges in an attempt to recover the precious metals. The one-cent and five-cent pieces are considered "minor" coins of the United States and have never contained precious metals, with the exception of the so-called Wartime nickels (from mid-1942 to 1945), composed of 56% copper, 35% silver and 9% manganese. Currently, none of the coins produced for circulation contain precious metals. However, the continued use of reeded edges on current circulating coinage of larger denominations is useful to the visually impaired. For example, the ten-cent and one-cent coins are similar in size; the reeding of the ten-cent coin makes it easily identifiable by touch.