<P> There are a few 1943 cents that were produced in bronze, as opposed to the steel / zinc composition used that year . There are 10 to 12 known to exist . Likewise, a few 1944 cents were produced in steel / zinc . </P> <P> In 1955, a hubbing error caused some cents to get struck with an obverse die which showed doubling in all of the obverse devices, producing a prominent doubling of the date, and to a less noticeable degree, the rest of the obverse . This is known as the 1955 doubled die cent . A similar die error occurred in 1969 on dies used at the San Francisco Mint . While the 1955 doubled die cent is well - known and widely collected, the 1969 - S doubled die is far rarer, with an uncirculated specimen selling for as much as $126,500 in a 2008 Heritage auction . The same mechanism produced 1972, 1983, 1984, and 1995 Doubled die cents . Doubled Dies are known for practically every date in the Lincoln cent series, but most are minor, and less impressive compared to the 1955 and the other Doubled Die varieties mentioned here . </P> <P> In 1990, 3,055 proof cents were struck at the San Francisco Mint without the "S" mint mark, making them appear as if they had been struck at the Philadelphia Mint . However, as no proof cents were struck in Philadelphia that year, they are easily distinguishable as errors, and highly valuable . </P> <P> The reverse of some Lincoln cents minted in 1992 at the Philadelphia and Denver mints and some of those minted in 1998 and 1999 at the San Francisco mint feature a smaller - than - normal gap between the first two letters of AMERICA . These coins, known as the Close AM variety are valued at $20,000 and $5,000 for the 1992 specimens in gem uncirculated condition and $3,000 and $1,000 for the San Francisco specimens in gem proof condition . </P>

When was copper stopped being used in pennies