Countermark

https://rpc.ashmus.ox.ac.uk/countermark/629 
GIC 503
?, 'cult symbol conposed of two crescents or sets of horns?'
rectangular with rounded corners 
8 x 6.5 mm 
possibly applied in area such as Edessa (Mesopotamia) or Dura 

Coins with this countermark

Number Image TypeNumber CoinNumber VolumeNumber
RPC II, 2021 Show 2021 49 2
RPC II, 2023 Show 2023 48 2
RPC II, 2016 Show 2016 20 2
RPC II, 2009 Show 2009 19 2
RPC I, 4307 Show 4307 11 1