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 off-metal sets.
Only 2 examples are known. Pollock lists both as being ex Brand, Farouk, Cox but the Farouk sale had only one of these. The other came from the Lohr collection. We cannot confirm that Brand ever owned these either.
The example illustrated above is ex Cox 2259, 66 ANA, Coronet Coin FPL #75, Champa-B/R lot 1057, Superior 10/89 lot 3270, Superior 1/94 sale as PCGS65RB, ANR's 8/04 as NGC67RB, Simpson collection - PCGS66RB.
The other, illustrated below, is ex Cox 2258, Coronet Coin FPL #74, Merkin 2/71, Champa-B/R 5/72 lot l058, Superior 10/89 lot 3271, Superior 5/90, ANR 12/03 and is in a PCGS64RED holder.
Additional sales listings for these include Pollock's 1992 sale price listing.
Photos of both courtesy of American Numismatic Rarities.