GIC 538: ΙΙΛ | SM (?) or ϹΛ, on a circular background (shield?)
Countermark: ΙΙΛ | SM (?) or ϹΛ, on a circular background (shield?) – as defined in C. Howgego, Greek Imperial Countermarks. Studies in the Provincial Coinage of the Roman Empire (London, 1985): no. 538