when did they start adding zinc to pennies
1864 1943 1864–1942
title: Penny (United States coin) text: Admiral Richard E. Byrd's expedition to the South Pole and Joe Louis. There was also a design featuring the Lord's prayer. Bronze, 1909–1942. Initially the alloy of the Lincoln cent followed that established for this denomination with the Indian Head design in 1864, 95% copper and 2.5% tin and 2.5% zinc. Wartime zinc-plated steel, 1943. The composition of the Lincoln cent was changed in 1943. Production of the war-time cent was provided for in an Act of Congress approved on December 18, 1942, which also set as the expiration date of the authority December 31, 1946. Low-grade carbon steel formed title: Penny (British pre-decimal coin) text: in production the alloy composition was changed to 95.5% copper, 3% tin, and 1.5% zinc, although the weight and size remained unchanged (which was necessary because of the existence by then of large numbers of coin-operated amusement machines and public telephones). Thereafter, pennies were minted every year for the remainder of George V's reign, although only six or seven 1933 coins were minted, specifically for the king to lay under the foundation stones of new buildings; one of these coins was stolen when a church in Leeds was demolished in the 1960s, and its whereabouts is unknown. A few pennies title: Penny (United States coin) text: restored. Bronze, 1947–1962. Shell casings were no longer used after 1946 and the original copper-tin-zinc "bronze" composition was again used. Brass, 1962–1982. The composition of the coin was changed again slightly in 1962. Mint officials felt that deletion of the tin content would have no adverse effect on the wearing qualities of the coin, whereas the manufacturing advantages to be gained with the alloy stabilized at 95% copper and 5% zinc would be of much benefit. Congressional authority for this modification is contained in an Act of Congress approved on September 5, 1962. Experimental aluminum cents, 1974. During the early title: Penny (United States coin) text: donated to the Smithsonian Institution. Another is in the hands of the family of a deceased U.S. Capitol police officer, known as the Toven Specimen, and was certified as authentic in 2005. Copper-plated zinc, 1982–present. In mid-1982, the coin's composition was changed again, this time to copper-plated zinc. The last mostly-copper cents (95% copper metal composition) were produced by the Denver Mint on October 22, 1982. The copper-plated zinc cent coins are still being produced today. They are composed of an inner core alloy of 99.2% zinc and 0.8% copper with an outer plating of pure copper, for an overall title: Penny (British pre-decimal coin) text: of Edward VIII exist, dated 1937, but technically they are pattern coins i.e. coins produced for official approval, which it would probably have been due to receive about the time that the King abdicated. Pennies were not minted every year of George VI's reign. Pennies minted in 1950 and 1951 were for overseas use only. One 1952 penny, believed to be unique, was struck by the Royal Mint. The worldwide shortage of tin during the Second World War caused a change in the alloy in 1944 to 97% copper, 0.5% tin, 2.5% zinc, but this bronze tarnishes unattractively, and the