I came across an odd nickel tonight. Looking for some of the fun S/S varieties ( http://varietyvista.com/05 JN RPMs/RPMs 1942S.htm ), I came across something that resembles a die break in the S. Could it possibly be a P/S?
I'm going with die chip. Well placed possibly. This all theory though. I'm part of the nightshift motley crew.
I think some of the P has been polished off (either at the mint or through wear). Alternatively, it could be a nickel sized S over a dime or penny S.