This copper Lincoln Memorial cent is a clashed cap strike, with a crisp, clear brockage of the Lincoln Memorial building overlaid over the top of the underlying late stage die cap strike's design. The error occurred when a late stage die cap came in contact with the reverse die, which imparted the central elements of reverse die's design onto the die cap. When this coin's planchet was fed into the striking chamber and struck, the resulting coin has the design of the original late stage die cap as well as the crisp, clear brockage from the "clashed cap." If you look closely, you'll see another "Lincoln Memorial" behind the obvious one, and you'll also see there is a blurry "UNUM" above the clear "UNUM."
NGC MS-63 BN