Although these are described as regular die trial pieces in the standard references, it is more likely that the off-metal 'trials' of this year were deliberately struck for sale to collectors.
Examples were struck as follows:
Copper J1170/P1312 with fewer than a half dozen believed to exist.
Aluminum J1171/P1313 with only 3 or 4 believed to exist
Nickel J1172/P1314 which is believed to be unique as a pattern. That piece is ex Woodin-1914 ANS exhibit, Newcomer, Farouk, Pine Tree 3/74, Paramount 4/77 and is a gem proof albeit weakly struck. There is a second example, in AU condition with a rotationally double struck reverse, ex Heritage 8/2001 ANA, Rau-Heritage 4/18 that may be a mint error struck on a shield nickel planchet.
Photo courtesy of American Numismatic Rarities.