With the claw mounts, it is almost certainly of German construction. With no maker or shop's name on the barrel, it is what is called a "guild gun." These are fairly common among all sorts of different firearms to include mauser actioned rifles. The term simply means it was built by an individual craftsman.
This one appears to have been assembled around a pure military action and barrel. It looks like a pretty good restocking job, and of course the mounts are a nice addition. Though I have never seen a front claw installed with such a large cap over the chamber. The original scope must have sat very high, which is why the military flag safety was retained. The only other obvious changes are a bit of shaping to the bolt and new open sights.
I am interested to hear other opinions about when it was built. The claw mounts and lack of scope would argue it may have been a thirties era rifle that was "liberated" by a GI and brought home. The scopes were normally kept in a separate leather scope carrier and were inevitably missed when the rifles were "freed" from Nazi tyranny. However, I have never seen a pre-war rifle with a military stepped barrel.
That leads to option number two which would argue for a rifle built during the occupation for a serviceman. There are many of those around, but I have rarely seen one with claw mounts. And had one been so built, in all likelihood, the scope would still be attached.
A mystery.
With the military livery, it is almost certainly a JS with a .323 bore size. But there is always the chance that it was made from an earlier rifle with the .318 bore. Have a gunsmith measure it for you while checking over the rifle.
JJ Perodeau can build you a set of rings to fit those bases.