Countermark

https://rpc.ashmus.ox.ac.uk/countermark/669 
GIC 540
ΚΑ
circular 
7 mm 
One on 'reverse' 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC IV, 6626 (temporary) Show 2905 1 4.3
RPC IV, 6631 (temporary) Show 2909 2 4.3
RPC IV, 6631 (temporary) Show 2909 1 4.3