In 2000 an unusual coin was found muling a Short Cross obverse of class VIa1 with a previously unrecorded reverse die reading +IOHANNESOND. The note publishes the coin and suggests the coin could be a pattern for King John’s Irish REX coinage. The author also discusses documentary evidence that leads him to suggest revised dates for the REX coinage.
A Pattern for King John’s Irish Coinage – Glenn Gittoes
BNS Research Blog 
An interesting article Glenn, but I’m wondering if the “D” at the end of the reverse legend could be inverted, and it is actually a coin of Iohan of Canterbury? Iohan is known to have minted in class Vc…. regards, Rob Page
Thanks Robert
Iohan of Canterbury did strike in early Vc, but the mint closed quite early in 1208, shortly after the provincial mints closed. The 4 London moneyers then produced vast numbers of class Vc coins for about two more years before class VIa1 began. Canterbury did not reopen until 1213. It seems difficult to explain why Iohan of Canterbury would produce a one-off coin in the middle of the period when the mint was closed and why it would be given an official VIa1 obverse die (which are only known for London) and a completely different style reverse. If it was Canterbury I would expect another example to have turned up by now.
The reversed C for D occurs on quite a few London dies in VIc1 as well as on the Irish coins – possibly it might even be the same die sinker. However, I can’t recall another example of the reversed C representing C in the Short Cross series.
Best regards
Glenn