What is the history of the 1944 penny?

Copper was a strategic war material needed for ammunition casings. Cents issued in 1943 were struck in zinc-coated steel to help free up copper supplies for the war effort. The steel cents proved unsatisfactory (rapid oxidation, confusion with dimes, etc.) so in 1944 copper coinage was resumed. Most of the copper was recovered from spent ammunition, so these cents were called "shell-case cents". Huge numbers were struck to help compensate for the steel cents that were being held as curiosities or lost due to rust, so the average 1944 cent does not command more than a few cents premium. However, in the flip side to what happened with the famous 1943 copper cents, in 1944 a few leftover steel planchets found their way into a press hopper and were struck with the 1944 date. They're not as well-known or as valuable as the '43 coppers but still retail in the thousands.