Countermark

https://rpc.ashmus.ox.ac.uk/countermark/638 
GIC 511
ΑΔΡ
rectangular 
6 x 3 - 3.5 mm 
GIC Countermarks book noted coins of Macrinus and Trajan; however, it is probable that all cases of ΑΔΡ on the Traianic coins were mis-readings of ΔΑΚ - GIC 529 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber