Georg, Thanks for taking the time, - although not as spectacular as the Simson (P08) or M95 sniper (your ongoing conversation with Andy as interesting as the rifle!), this is just as fascinating in my book.
You can see the faint old serial on the receiver lined through, though the fireproof is very unclear, - while this rifle has been through a lot, it really is fairly typical of these, they are almost never in good condition, interestingly several are also bond drive rifles which indicate that these probably made it to the front line early and were captured in some number (enough to show up in US bond drives), I owned a CGH much like this one, though prettier, MauserBill reactivated it and although not a full matcher, it is pretty original.
This variation is one of the most interesting ones encountered during the war!