Earlier today I saw a post about wheat pennies which brought me to a search about other wheat pennies. I found a collection that looked like it had a silver pennies and found out that they are made of steel. I was hoping some people could clarify why there were steal pennies and if it had anything to do with WWII? (Just a guess based on the timing).
Wars always have a way of impacting the money supply, something the study of numismatics, can provide insight into. Unlike today's penny or one cent coin which are 97.5% zinc and 2.5% copper the pre-war penny was 95% copper. Copper has a myriad of uses and military applications, most commonly ammunition. Due to this, the mint changed the composition of the penny to zinc-coated steel. Your guess of WWII was completely correct!