A.F. Basset Hull, in Vindin’s Philatelic monthly, 20 February 1894, wrote regarding the die for this Duty stamp: "From this die Mr Knight prepared 120 electros, arranged in 12 horizontal rows of 10 stamps." Ever since, writers have assumed, quite wrongly, that 120 separate electros were used for the printing plate.
A study of this stamp shows that, just as for the postage stamps which followed, William Knight used a working die of a "group of four" to produce 30 electros to form the plate of 120 subjects.
In June 1994 of the same journal, on p. 39, he provided this update: