This 1979-D Lincoln cent is a deep obverse die cap, with a high cap wall around the obverse design. The die cap is so deep that the PCGS slab has cracks on both sides of the holder! The error occurred when this cent stuck to the obverse die when it was strike, and the proceeded to be struck into multiple income planchets, forcing the coin's metal to flow outward and upward around the die's neck. A dramatic and popular error type.
PCGS MS-64 Red. Note: There are some obvious, scuffy, cloudy marks which are on the holder, not the coin on both sides.