Countermark

https://rpc.ashmus.ox.ac.uk/countermark/233 
GIC 110
laureate head r.
circular 
7 mm 
Noted on coins of Ancyra (Galatia) and Pessinus, so possibly might have been applied at Pessinus? Possibly connected with Caracalla's journey to the east in 215. 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber