OK, here is my $0.02 worth, The "curious cross hatch pattern" on the bottom of the barrel seems to me to be Vise jaw imprints.The unusual milling cut on top of the barrel, seems to be to remove the opposite vise jaw imprint. There are also milling cuts on the sides of the barrel, which may be there to remove another set of vise jaw imprints. The eagle mark on the top of the barrel, seems to be a Bundesadler, which would be post WW2, after the Germans regained control of their country. This seems to be a rifle put together after the war, using available components. This, itself, would not be enough to make me afraid to shoot it.
Mike
