Countermark

https://rpc.ashmus.ox.ac.uk/countermark/826 
GIC 707
uncertain inscription (contraction for Σεβαστόν?)
rectangular with rounded corners 
10.5 x 3.5 mm 
compare with https://rpc.ashmus.ox.ac.uk/countermark/1241 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 1435 Show 1435 4 1
RPC I, 1434A Show 1434 1 1