Hello Forum. The moderator Richard had to help me get on here. I just have two coins that I would like your opinions on. They are two 1943 d pennies. Both look strange and would like to put them to rest. One has two colors. the typical newer steel penny look with some brass present and some signs of rust. A few edge issues. The other looks very good but with a half circle stain on it. Other than that it looks perfect to me. I had inherited this group of coins from my father that had served in WW2. I do not expect any value to these but I want to put them out there for your viewing. There are many foreign coins with this grouping. Thanks for inviting me on to this forum.
I don't know why some of these were re-plated. Perhaps to re-sell as novelties i.e. war pennies as you mentioned. Most people would prefer a shiny coin and wouldn't think about them not being original as issued by the mint.
If you have War Nickels, those are 35% silver and worth $1.50 each at a minimum. You can tell War Nickels 1942-1945 because they have a large mintmark on the reverse over the dome of the Jefferson Memorial.
To the OP.. As just_carl said many people plate coins for many reasons. Wouldn't recommend plating most coins as doing so would dramatically reduce their value.Your coins are a nice link to your father's war service. Keepers for sure in any condition.