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 aluminum sets.
Only 2 are known as follows:
1) Gschwend, Brand, unknown intermediates, Boosel-RARCOA 4/72, RARCOA 1/73, Stacks 1/87, Superior 10/90, Bowers and Merena 11/92, Bowers and Merena 1/97, ANR 7/05 - illustrated above and easily matched to the Gschwend sale plate. Click on the thumbnail image for an enlargement.
Photo courtesy of American Numismatic Rarities.
2) Cox-Stacks 4/62 now in the Smithsonian and illustrated below.
Photo courtesy of the National Numismatic Collection of the Smithsonian Institution.
Additional listings for these include B.G. Johnson 7/16/41 invoice to Boyd and 8/13/41 invoice to Kelly.