Countermark

https://rpc.ashmus.ox.ac.uk/countermark/465 
GIC 345
owl standing facing, wings closed
circular 
7 mm 
It might be a countermark of Ilium cf. Oxford 1244-5 and GIC 346, but that is no more than speculation 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 1656 Show 1656 23 1
RPC I, 1657 Show 1657 36 1
RPC I, 2238 Show 2238 2 1
RPC I, 1656 Show 1656 120 1