I have a 1946 S Wheat Cent with an interesting mintmark. Photos 1, 2 and 3 are the coin in question. This appears to be a re punch maybe. It looks like it could possibly be a sans serif S over an inverted S? Let me hear your opinions. Photos 4 and 5 are another 1946 S that I found, the inverted S variety. That will give you a comparison for the inverted S.
I would look here for an RPM. Seems to be a few. http://www.varietyvista.com/02a LC RPMs Vol 1/RPMs 1946S.htm
Thanks alurid. I have looked through Variety Vista and Coppercoins. I didn't find anything that was a match.
I can't find a match in Wexler's list either. It looks like an RPM to me, but maybe it isn't. I don't know.