Looks like damage from something. Notice how it even pushes in the inner edge of the rim, and is a consistent depth and smoothness in a way going up and down on the lower part of the T then up and around. Kinda looks like a bend staple smashed on it. but the experts may have a better idea ...
That is a nice example of a Struck Through foreign object. I'm guessing it is a wire bristle. There have been wire bristles, staples, strings, cloth and different objects that are hard enough to leave an incused impression in the surface of coins. http://www.error-ref.com/struck-through_wire/
Interesting. At first glance it appears to be damaged. But there is no sign of the metal being moved. Possibly a struck through.
