Countermark

https://rpc.ashmus.ox.ac.uk/countermark/1724 
GIC —
B? (or possibly Θ)
circular 
5.5 mm 
Uncertain (Uncertain)
GIC 770 is also a B, but only appears on coins of Hadrian 
List of countermarks View on a map

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC VI, 9376 (temporary) Show 9329 9 6