Countermark

https://rpc.ashmus.ox.ac.uk/countermark/1175 
GIC
K or AT or IE?
incuse in square shape 
5 mm 
 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 758 Show 758 3 1
RPC I, 759 Show 759 5 1
RPC I, 759A Show 759 2 1
RPC I, 758 Show 758 6 1