Countermark

https://rpc.ashmus.ox.ac.uk/countermark/1586 
GIC
concentric circles?
circular 
2 mm 
might possibly be a shield? 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 1104 Show 1104 29 1
RPC I, 1104 Show 1104 32 1
RPC I, 1104 Show 1104 31 1