Despite the production of over a billion coins in 1943 by all US mints the Steel penny remains a fairly common collectible. Different steel penny versions became rare and expensive during 1943 but copper penny errors stand alone as the rarest and most valuable among them all. People who collect these coins will find steel pennies in excellent shape as valuable assets. Coins with mint mark letters especially ‘S’ for San Francisco and ‘D’ often sell for more money. A coin’s rarity depends on how well it was preserved plus what minting details it has including special mistakes.