I forget where I saw it! LOL It might not have been this forum even. Coop nailed it and even made one of his famous pictures of it.
A tapered planchet is just a planchet that is thinner on one side than it is supposed to be. Usually happens at the end of the strip. I'd be more inclined to go with that than I would grease filled die for this coin. And I see no signs of damage that could cause it. Meaning the coin was not ground down. Yes, the coin is damaged, but not from grinding. It's scratched.
An image of the rim area in question may help. Nut it could be another date with that much missing from the date area.
thin planchet After reviewing the thread, I pulled out the micrometer. The rim on the "weak" side is 1/32" thinner, compared to the opposite side. Thanks for all input.