Thanks to Alice Lyons our RB pottery specialist the lovely stamped mortarium sherd was conveyed up to Leeds and subjected to the expert attention of Kay Hartley (Kay Hartley Mortarium Archive Project). As an aside, Kay’s archive of mortarium stamps assembled over decades is currently in the process of being digitised.
Kay confirmed that the stamp is of the Caistor potter NATIO AD 120/150 and she has at least six examples recorded. We are aware of two examples in the Norfolk Museums collection. Interestingly the stamped mortarium sherd was recovered from Trench 9, the location of the kiln, the stoke hole of which was uncovered at the southern end of the trench