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 in complete sets.
Examples were also struck as follows:
Copper J1227/P1370 with only 3 or 4 known.
Aluminum J1228/P1371 with about 2 or 3 known.
Silver J1229/P1369. This is unique and is ex Newcomer, Farouk, Kreisberg 2/60, Federal Brand 10/61, Federal Brand 1/62, Boosel-Rarcoa 2/72. If it is not a silverplated copper example, then it might be a mint error struck on a trime or half dime planchet.
Photo courtesy of Heritage.