Countermark

https://rpc.ashmus.ox.ac.uk/countermark/459 
GIC 339
eagle r. or l., head l. or r.
circular 
7–8 mm 
As 339i and 339ii. GIC suggested that the countermarks were applied no later than Gallus, but subsequent examples are on coins of Valerian, Gallienus and Salonina. 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC VII.2, 3110 Show 3110 9 7.2
RPC VII.2, 3021 Show 3021 8 7.2
RPC VII.2, 2997 Show 2997 5 7.2
RPC VI, 7078 (temporary) Show 6648 2 6
RPC VI, 7137 (temporary) Show 6668 5 6
RPC VI, 7137 (temporary) Show 6668 4 6
RPC VI, 7113 (temporary) Show 6691 3 6
RPC VI, 7091 (temporary) Show 6649 1 6
RPC VII.2, 3023 Show 3023 1 7.2
RPC VI, 7105 (temporary) Show 6686 6 6
RPC X, — (number not assigned), type ID 88146 Show 4133 1 10
RPC X, — (number not assigned), type ID 88264 Show 4129 1 10
RPC X, — (number not assigned), type ID 60599 Show 4137 5 10
RPC VI, 7091 (temporary) Show 6649 10 6