Although described as regular dies trial pieces in the literature, these were actually deliberately struck for sale to collectors as part of complete off-metal sets.
Examples were struck as follows:
Copper J1087/P1223 with about a half dozen known.
Aluminum J1088/P1224 with fewer than 3 confirmed.
Nickel J1089/P1225 with the illustrated example, from Superior's 9/02 sale, believed to be unique and formerly in the Dunham and Farouk sales.
Photo courtesy of Superior.