Countermark

https://rpc.ashmus.ox.ac.uk/countermark/782 
GIC 657
monogram TR?
circular 
4.5 mm 
Tr(oas)? Sometimes on reverse 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 1656 Show 1656 25 1
RPC I, 1657 Show 1657 12 1
RPC I, 1656 Show 1656 97 1
RPC I, 1656 Show 1656 103 1
RPC I, 1656 Show 1656 119 1
RPC I, 1656 Show 1656 124 1