Because of the problem with corrosion and rust many steel pennies have been reprocessed which means they have been re-plated with zinc.
One thing I question about that is if they would lose numismatic value because they are not original?
Reprocessing involves stripping off the old zinc, removing any rust from the surface of the coins, and electromagnetic reprocessing re-coating them in zinc, giving them a shiny finish. This was done by others and not the mint.
How to tell if your coin has been re plated/reprocessed
The color is bluish and extremely shiny on the reprocessed ones. Original 1943 cents have a nice cartwheel luster to them, and if you hold them side by side with a reprocessed one, the difference is readily apparent.
Re Plated Original

The original blanks were punched from zinc plated steel core, the edges of an original would show steel edges rather than zinc. Reprocessing plates all surfaces, including the edges.