Countermark

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

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC IV, 6626 (temporary) Show 3011 1 4.3
RPC IV, 6631 (temporary) Show 3015 2 4.3
RPC IV, 6631 (temporary) Show 3015 1 4.3
RPC IV, 6631 (temporary) Show 3015 3 4.3