Yes, the range drum markings are unusual. I've never seen one graduated up to 1100 before. As you say, 600 is the standard. The rifle has been made up, although in my estimation, the parts are all genuine. The 5 BA screws are wrong (cheese heads were used, but the tops were slightly rounded, resembling the shape of a pork pie in section!). These look to have been inserted relatively recently & have been left flat topped. There is also evidence of milling of the receiver side wall to produce a suitable mating surface for the base. The originals were hand scraped & filed to suit. That may sound counter-intuitive, but I've seen a few rifles now over the years with the bases removed & all were done like this. And of course, a 1918 dated rifle immediately puts one on one's guard......