Countermark

https://rpc.ashmus.ox.ac.uk/countermark/772 
GIC 649
monogram IMP
rectangular 
variable c. 8 x 5 mm 
Imp(erator); Pangerl 79; Pangerl assigns to Pannonia, FITA to Provincia Asia and Waddignton to Bithynia. GIC suggests that it was probably applied in Europe. 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 2235 Show 2235 48 1
RPC I, 5422 Show 5422 1 1
RPC I, 2235 Show 2235 58 1
RPC I, 2235 Show 2235 57 1
RPC I, 2235 Show 2235 56 1
RPC I, 2235 Show 2235 59 1