This is the famous 1976 bicentennial half dollar struck in proof on a 40% silver clad planchet without the "S" mintmark.
Several of these were issued in sets along with the quarter J2161/P2085 and dollar J2163/P2087.
According to Pollock, President Gerald Ford and his appointment's secretary received sets. It is not known if these or any other sets are still in existence.
Photo has been modified from the set in Stacks 5/2001 sale.