I have had this stamp a while and suspected that it was from plate 172. With it's strong linear TRL and general appearance screaming second state it was plated rather than be put into the "Mispef" area. 172 was confirmed by the nice block of 4 from Kevin Maunder.
I have also shown the imprimatur for AL which shows just how much the A check letter has been thinned in state two.
AP
October 2020