This new listing caught my attention: http://www.ebay.com/itm/UNREAL-STRI...E-1921-MORGAN-SILVER-DOLLAR-VAM-/361210214937 The date is very weak, but there's corresponding weakness through STATES OF on the reverse. Is this common in struck-through-grease examples? It makes me think of a planchet that's thin along one side, but I don't know whether that even happens, and if it does, I don't know if this is what the result looks like...
There is a type of rolling mill error called a tapered planchet, but I don't know the diagnostics, and error-ref.com doesn't have images up yet.