Countermark

https://rpc.ashmus.ox.ac.uk/countermark/683 
GIC 554
ΝΙΚΟΜΗΔ
rectangular 
5.5 - 6.5 x 2 - 2.5 mm 
Has been attributed to Cos, due to association with the GIC 355 Crab on the coin in Emerkingen, but might also be Nicomedia 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC I, 1656 Show 1656 64 1
RPC I, 1656 Show 1656 99 1