Countermark

https://rpc.ashmus.ox.ac.uk/countermark/644 
GIC 517
ΑΡΙ
rectangular 
6 x 2 mm 
Aristos. Bellinger (Dura p.155) was probably right that these coins were struck in AD 114 (when the title Optimus was assumed) and that the title was missing from some. 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC III, 3447 Show 3447 2 3
RPC III, 3447 Show 3447 3 3
RPC III, 3447 Show 3447 1 3
RPC III, 3447 Show 3447 6 3
RPC III, 3447 Show 3447 7 3
RPC III, 3447 Show 3447 8 3
RPC III, 3447 Show 3447 9 3