Although described as regular dies trial pieces, this was deliberately struck for sale to collectors as part of complete off-metal sets.
Examples were struck as follows:
Copper J760/P845 with fewer than a half dozen known.
Photo courtesy of Ira & Larry Goldberg's Coins & Collectibles.
Aluminum J761/P846 with fewer than a half dozen known.
Nickel J762/P847 with apparently 2 known including the B/M 9/01 - NGC64 which is illustrated below and Simpson-Heritage 11/20 - PCGS66 examples. One of these probably accounts for the one in Bowers and Ruddy's 12/75 sale.
Photo courtesy of Bowers and Merena.