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 4 or 5 were struck in copper.
These were also struck in aluminum J1437/P1580 with only 2 or 3 believed to exist.
The die trials of this date often have been gilted due to the extreme rarity of its gold counterpart.
Photo courtesy of Stacks.