Although described as regular dies trial pieces, these were actually deliberately struck for sale to collectors as part of complete off-metal sets.
In aluminum, as illustrated, 4 or fewer are believed to exist.
Copper J1183 with only the cleaned Farouk example analyzed and confirmed as being pure copper. It was last offered in Heritage 5/09 sale. If any others exist, they are probably masquerading as a regular issue proof.
Photo is of the former J.E. Drew example.