https://rpc.ashmus.ox.ac.uk/countermark/1712 

GIC —

ΛΑ? incuse

incuse 

c. 8 mm wide x 5 mm tall 

Cyzicus (Mysia)

possibly not a cmk, since it invites comparison with the Christian graffiti, including a chi-rho monogram, on a coin from Caracalla from the same mint (M. J. Price Coins and the Bible, 1975, p.28) - see GIC 439