Countermark

https://rpc.ashmus.ox.ac.uk/countermark/622 
GIC 497
radiate bust, facing
square 
3.5 mm 
GIC had "?, 'helmet' (perhaps a facing radiate bust)". Further specimens seem to confirm the "facing radiate bust" 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 3356 Show 3356 3 1
RPC I, 3356 Show 3356 6 1
RPC I, 3356 Show 3356 19 1
RPC I, 3356 Show 3356 20 1