Kinda looks like something to do with the zinc split plating . Maybe a close up of the D would tell better.
Here's a pic of a Jefferson nickle I found minted with a worn die - called Die Deterioration Doubling (DDD) - fun to find but not really worth any more than face value.
Check the edge to see if you can still see the steel core, if not, it was reprocessed ( plated ) after leaving the mint ( many, many were), and if not well cleaned, debris and corrosion was covered over and led many to suspect plating errors at the mint, when they were PMD.