NGC 50c 1971-S proof Kennedy half with strong clashed dies on the obverse and reverse. The clash marks can be seen around Kennedy's profile, and the outline of much of Kennedy's head can be seen on the coin's reverse.
Proof coins are made with high quality controls, and clashed dies are quickly removed from the press. Proof coins with clashed dies, especially strong clashed dies are generally very scarce.
PF64 with brown toning.