I've been working on this one for a little while and can't seem to quite nail down exactly what it is. Any help would be appreciated!
From what I can make out from the obverse legend, I narrowed it down to the following possibilities:
Henry III - 6C or 7
John - 5B/5C/6A
Richard I - 2/3A/4B
It looks like the mint maybe be Canterbury. If the last two letters before Canterbury are "ON", the only possibility that could match that I came across would be Simon on the Henry III Class 7.
Here are my photos as well as a sketch of what I can make out on the reverse:



