Countermark

https://rpc.ashmus.ox.ac.uk/countermark/956 
GIC 842
laureate bust r., letter before (Ϲ, Ο, or Κ) (on silver coins)
On silver coins 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC III, 3257 Show 3257 4 3
RPC III, 3257 Show 3257 71 3
RPC III, 3257 Show 3257 8 3
RPC III, 3257 Show 3257 5 3
RPC III, 3257 Show 3257 16 3
RPC III, 3257 Show 3257 17 3
RPC III, 3257 Show 3257 10 3
RPC III, 3257 Show 3257 65 3
RPC III, 3257 Show 3257 2 3
RPC III, 3257 Show 3257 11 3