Found this in a roll of 1941 cents, looking for a DDO. No DDOs, but I did find this. Ugly and covered in spots and corrosion, but I found the error to be interesting so I decided to post it. Weighs 2.8 grams, and has obvious weakness on both the obverse and reverse. I thought 2.8 might be within mint tolerance, but I couldn't think of any error that would be like this besides a rolled thin planchet.
I would disagree with the grease strike opinion. On the obverse and a little on the reverse, the rims are also affected by the weakness which leads me to believe this is indeed a rolled thin planchet. A strike through grease would not make the rims weaker.
Collector of U.S. Coins, Varieties, and Colonial Coinage