Countermark

https://rpc.ashmus.ox.ac.uk/countermark/77 
GIC 790
denominational mark Δ
Square punch 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC IX, 486 Show 486 1 9
RPC IX, 508 Show 508 1 9
RPC VII.1, 53 Show 53 6 7.1
RPC VIII, — (number not assigned), type ID 20127 Show 928 2 8
RPC VIII, — (number not assigned), type ID 20182 Show 1106 5 8
RPC VI, 4014 (temporary) Show 3360 15 6