Although described as regular dies trial pieces, these were actually deliberately struck for sales to collectors as part of complete off-metal sets.
Examples were struck as follows:
Copper with reeded edge J821/P911 with only 3 or 4 believed to exist.
Copper with plain edge J822/P912. We have not been able to confirm its existence.
Aluminum with reeded edge J823/P913 with only 2 or 3 believed to exist.
Nickel with reeded edge J824/P914 with only the former Farouk coin believed to exist.
Photo courtesy of American Numismatic Rarities.