It's not class 5; the portrait looks more like class 7 to me. I'm pretty sure that the reverse legend is IOAN ON CAN.T so it couldn't be class 5 anyway.
Slevin's Short Cross Legends has a 7b2 with that exact reverse legend, but the A in CANT looks more like 7a (pointed) than 7b (vertical sides) than that example. Bizarrely placed reverse pellet stops are very common in classes 7a3 and 7b, so without a better ID of the portrait I can't be sure on the class, but the portrait looks more like a 7b to me, so it may be a 7b1/7a3 mule. Oh and Henry III, not John.
Anyone else fancy a go?