Although described as a regular dies trial piece in aluminum, these were actually deliberately struck for sale to collectors as part of complete sets.
Examples were struck as follows:
Copper J1047/P1181 with fewer than a half dozen believed to exist.
Nickel J1048/P1182 which is believed to be unique. This may be a mint error struck on a 3 cent nickel planchet.
Aluminum J1049/P1183 with only 2 or 3 believed to exist.
Photo courtesy of Heritage.