Countermark

https://rpc.ashmus.ox.ac.uk/countermark/1385 
GIC
bearded male head r.; on obverse
oval 
4.5 x 3.5 mm 
Haymann noted a cmk on a coin of Haymann 20b; noted as Hadrian? 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC II, 1770 Show 1770 5 2
RPC II, 1770 Show 1770 7 2
RPC II, 1770 Show 1770 10 2