Although described as regular die trial pieces in the standard references, these were actually deliberately struck for sale to collectors as part of complete off-metal sets.
Examples were struck as follows:
Copper J1210/P1350 with the following 2 known.
1) Stacks 9/92, Lemus-Queller, Heritage 1/09 as NGC65BN, Simpson collection - PCGS65BN, illustrated above
2) Bolender 11/59, Merkin 9/68, Kentucky collection, various greatcollections.com weekly auctions - NGC66RB
Aluminum J1211/P1351. with fewer than 3 examples known
Photo courtesy of Heritage.