This 1991P Lincoln cent has a radical misaligned die clash (MAD), which more than likely occurred during the installation of the dies. The overlay shows the relative position of the dies when they did clash.

The image to the left shows a magnified view of the clash mark left by the reverse die under the Y of LIBERTY.

A magnified view of the area involved shows the slight curvature to the clash mark and the straight edge left by the top of the U in UNITED.