The planchet is thicker than normal, weighing 4.04 grams instead of the proper weight of 3.1 grams. Much thicker visually, and also the coin has very strong strike due to the increased thickness of the planchet.
The error may have occurred due to having been "rolled thick" during the planchet strip rolling operation, but it is unclear what the exact cause was. A neat error on a WWII era cent.
NGC MS-64 Brown