Steel pennies were minted in 1943 because of Word War II. Copper was needed for the war effort, so production on copper pennies was halted. The U.S. Mint created the copper penny with a zinc-coated steel replacement that is an interesting coin but not rare for numismatists.
During the height of the United States' involvement in World War II, there was a shortage of copper for use in ammunition and other equipment. This forced the U.S. Mint to come up with a replacement material to make the penny.
The steel penny was struck only in 1943. A few rare 1944 steel pennies exist because of an error at the Mint during the 1944 striking.
Steel pennies were minted in all three Mints: Denver, San Francisco and Philadelphia. Pennies minted in Denver and San Francisco are marked with a "D" or "S" below the date.
An original 1943 steel penny is not considered a rare U.S. coin. The value of the coin ranges from 10 cents for circulated condition up to £45 for near-perfect, uncirculated condition.
A 1943 steel penny is the only regular-issued coin that can be picked up by a magnet. It is also the only coin not containing copper to be circulated.