Countermark

https://rpc.ashmus.ox.ac.uk/countermark/876 
GIC 742
denominational mark S
rectangular 
As 742i and 742ii 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC III, 1765 Show 1765 4 3
RPC III, 1765 Show 1765 13 3