I can spot areas of tooling/smoothing on the reverse just left of the eagles neck/under the eagles chin, as well as tooling/smoothing above the eagles head/under the letter "E" in STATES.
The stars look very sharp, I'm surprised it didn't get a UNC details grade. As others have stated, the coin is not a proof as the reverse die crack above the "ED" in UNITED would have taken thousands of strikes with that die before such a failure to occur.