DWM 1917 Arty Proof mark ?
 

Friend has a DWM 1917 Artillery SN "8319" suffix "i", with TSS proofs on right side and what seems like an "iron cross" like stamp on the same side on the barrel.


Does anyone know what the "iron cross" stamp represents and how common it might be.


The "8319" serial is getting very close to end of production run.


Regards;