Countermark

https://rpc.ashmus.ox.ac.uk/countermark/153 
GIC 33 i
ΖΜΥΡ, bearded bust r., ? laureate
circular 
7 mm 
The form Z was used on coins of Smyrna until the time of Hadrian 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
Show 11