Normally will tell you right away. This is an original with the zinc coating oxidising, but the edge is rusting steel
Poor things oxidized really quick. At least the mint was able to use some of the leftovers as Belgian 2 Franc pieces. I always wondered if metals were so needed for the war why the country didn't suspend production. Surely there were enough in circulation. Since I mainly collect world coins, there are many instances where issues are paused for a year or more before minting resumes.
Back in 1943, the cent was more important than you might imagine. The economy was also far more active than it had been during the Great Depression. The last thing the wartime economy needed was a coin shortage to gum things up. The mintages had been way down during the depression. There weren’t that many new coins in circulation.
I do not agree with your statement 100%. But as a blanket/rule of thumb type of statement for newer and unskilled collectors it does give a correct message to use caution when dealing with these one year only coins that are so much different than the common copper counterparts. There are zinc plated steel cents that do qualify for a brilliant uncirculated designation. I have seen steel cents with original surfaces that will reflect what is called the cartwheel effect. They could be described as bright and shiny. Because the surface of these coin are so susceptible to damage from just mere handling and being around 80 + years, coins of this type that have a BU appearance are not and will not be commonly found, they will most likely have to be purchased outright if a higher grade specimen is desired. As a 50 year+ Lincoln cent collector the 1943 cent with original surfaces and no rust has been and still is one of the hardest coins to find in higher grades.