Countermark

https://rpc.ashmus.ox.ac.uk/countermark/1401 
GIC
VAR monogram
rectangular 
monogram is different from GIC 658 or GIC 659 types and is applied to an imperial coin. It might (or might not) referd to P. Quinctlius Varus 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber