From PCGS Library

"To date only five 1968-S Proof half dollars
with inverted Mint marks have been found"

by Ken Potter - March 12, 1999

---

The Top 50 U.S. Coins of All Time

by Ed Reiter - December 27, 1999

---

A Clad-Edged Investment

by Ed Reiter - November 19, 1998

---

------------------------------------------------------------------------------------------------------------------------------------------------------------