Artillery Luger questions

[Cranel]

I recently received a Luger from my father, he's had it for at least forty years that I know of an never touched it. I have quite a few guns and know Broomhandle and other collectables fairly well. Enough of that. This Luger has no numbers or proof marks anywhere. It has a cut out in the back where a strap would go but no signs of ever having the bar to attach it to. The barrel is more of a straw color than the rest of the gun with no marks on it. The finish seems to be about 85 percent maybe more. It has an adjustable rear sight (elevation) but no numbers or proofs at all? The grips have wear that would be consistent with age and they have no stamps either. Any ideas ??? Also it does not have a grip safety and appears to have a "0" under the safety lever