Charles E. Barber's famous 1891 Liberty half dollar pattern. This design as illustrated went into regular production the following year but with a different reverse without the clouds above the eagle.
This particular reverse design is similar to the one used on J1762/P1976 but contains smaller eagle, stars and clouds.
Only 2 are known and both are in the Smithsonian.
Photo courtesy of the National Numismatic Collection of the Smithsonian Institution.