Although these are described as regular die trial pieces in the standard references, it is more likely that these were deliberately struck for sale to collectors as part of complete off-metal sets.
Examples were struck as follows:
Copper J1270/P1412 with about 4 or 5 believed to exist, 2 of which were in Heritage 11/03 sale.
Aluminum J1271/P1413 with about 2 or 3 believed to exist, from the Farouk and/or Lohr collections, one of which is illustrated below.
Photos courtesy of American Numismatic Rarities.