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 in complete sets.
Examples were also struck as follows:
Copper J1448/P1593 with about 4 or 5 known.
Brass P1594. Pollock mentions the Farouk coin had brassy toning. We believe it is the same as the copper above.
Aluminum J1449/P1595 with only 2 or 3 known.
Note: The die trials of this year are often found gilt due to the extreme rarity of many of the gold denominations.
Photo courtesy of Superior.