Countermark

https://rpc.ashmus.ox.ac.uk/countermark/664 
GIC 534
ΔΧ or ΧΔ
oval 
8 x 6 mm 
Applied at Anchials or Apollonia. 4 chalcoi? 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC IV, 4533 (temporary) Show 2462 7 4.1
RPC IV, 4532 (temporary) Show 2461 3 4.1