Countermark

https://rpc.ashmus.ox.ac.uk/countermark/694 
GIC 568
ΤΟΝΖΟΥ
rectangular 
13 x 3 mm 
The Tonzos was a river in Thrace. Its personification appeared on the coins of Harianopolis. The countermark might have been applied there to "validate" the coins of other cities 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC II, 628 Show 628 17 2
RPC III, 1154 Show 1154 7 3
RPC III, 1160 Show 1160 3 3
RPC III, 1154 Show 1154 12 3
RPC III, 1124 Show 1124 2 3
RPC III, 1148e Show 1148 3 3
RPC III, 1047 Show 1047 3 3
RPC III, 1154 Show 1154 15 3
Show 52
Show 81
Show 77
RPC III, 1606A Show 1606 1 3