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 as part of complete off-metal sets.
Examples were struck as follows:
Copper J1272/P1414 with only 3 or 4 known including the illustrated piece, ex Superior 1989 Heifetz sale, and the McCabe, Clapp family, Eliasberg-B/M 5/96, Simpson-Heritage 11/20 - PCGS67BN coin.
Aluminum J1273/P1415 with only 2 or 3 known.
Photo courtesy of Superior and is believed to be the Lohr-Cox coin.