Countermark

https://rpc.ashmus.ox.ac.uk/countermark/811 
GIC 690
Φ
circular 
5 mm 
Φ may have referred to the city, Philippi, before it was renamed Neronias by Agrippa II (after Neronias it was called Paneas). Alternatively, the letter may have stood for the name of Herod Philip II. 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 4942 Show 4942 4 1
RPC I, 4942 Show 4942 8 1
RPC I, 4942 Show 4942 9 1
RPC I, 4943 Show 4943 16 1
RPC I, 4943 Show 4943 20 1
RPC I, 4943 Show 4943 21 1
RPC I, 4943 Show 4943 22 1
RPC I, 4943 Show 4943 23 1
RPC I, 4943 Show 4943 24 1
RPC I, 4943 Show 4943 4 1
RPC I, 4943 Show 4943 10 1
RPC I, 4943 Show 4943 11 1
RPC I, 4943 Show 4943 1 1