The physical specifications of U.S. coins—metallic content, weights, diameters—have been ever changing. Changes were in response to increases and decreases in metal prices, public rejection of large-diameter coins, and other factors.
Even before the first copper coins were struck in 1793, their weights were reduced under the Act of May 8, 1792. The modified weights are 6.74 grams for the half cent and 13.48 grams for the cent (weights are given in grams for modern convenience; the early coinage laws specified the weights in grains). Weights for both copper coins were reduced in 1795, to 5.44 grams for the half cent and to 10.89 grams for the cent. The 1794 and 1795 silver coinage was struck in a composition of 90 percent silver and 10 percent copper, according to some sources. When additional silver denominations were added in 1796, the composition for all five coins was changed to 89.2427 percent silver and 10.7572 percent copper, until additional change came in 1836 and 1837.
Composition of the first gold coins is 91.6667 percent gold and 8.3333 percent copper and silver.
The only changes made to U.S. coins from the first decade of the 19th century to 1834 were to the designs. Then, on June 28, 1834, the weight of gold coins was reduced and the alloy changed for two years to 89.9225 percent gold and 10.0775 percent copper and silver. In 1836, the gold alloy was changed again, to 90 percent gold and 10 percent copper and silver, an alloy unchanged until 1873. Changes were made to silver coins in 1836 as well, when the silver content was changed to 90 percent silver and 10 percent copper, an alloy used until the mid-1960s.
The rising price of silver resulted in a reduction in weights for the silver coins during 1853 (except for the silver dollar). Arrows were added to both sides of the dates on the reduced weight half dimes, dimes, quarter dollars and half dollars, a design feature used for 1853 and 1854. The arrows were removed in 1855 although the weights of the coins remained the same.
Major changes were made to the country’s copper coinage in 1857. The half cent was eliminated and the large copper cent was replaced with a smaller cent composed of 88 percent copper and 12 percent nickel (Act of Feb. 21, 1857). Diameter of the old cent is approximately 29 millimeters; the new cent has a diameter of 19 millimeters. A bronze cent and 2-cent coin were introduced in 1864.
The weights of the Seated Liberty silver coinage were increased in 1873, and once again arrows were placed at either side of the date to signify the increased weight. Also, silver was dropped from the gold-coin alloy, which was changed to 90 percent gold and 10 percent copper.
The next major compositional changes in U.S. coins were made during World War II. At the beginning of the United States’ entry into World War II, several metals used in coinage became strategically important to the war effort. The first to be affected was the 5-cent coin, which had nickel removed starting Oct. 8, 1942, when 5-cent coins in a new composition—56 percent copper, 35 percent silver and 9 percent manganese—went into production. Use of the copper-nickel alloy was resumed in 1946.
Also during the war, the cent composition was changed. First, tin was removed sometime late in 1942. Then, in 1943, a zinc-coated steel cent was introduced to conserve copper. The brass alloy of 95 percent copper and 5 percent zinc resumed in 1944 through 1946. The 95 percent copper, 5 percent tin and zinc composition resumed in 1947 and continued until late 1962 when, once again, tin was removed from the bronze alloy, returning the alloy to the same composition, called brass, used in 1944 to 1946.
The 175-year-old history of United States coinage was changed with the stroke of a pen on July 23, 1965. On that day President Lyndon Johnson signed into law the Coinage Act of 1965, representing the most sweeping changes to the U.S. coinage system since the Mint Act of 1873. The 1965 act eliminated silver in dimes and quarter dollars and reduced the silver content of the half dollars to 40 percent.