That is the top grade Noske A with screwon adjustment caps. A cheaper B with the same optics (I think) but no caps was also made. These were the last Noske models. On thr A, you zeroed at 100 then set the disc at 100 tightened it and then turned the disc for the range of the target. Never tried to see how well it worked. Adjustments on the A were advertised as handmade. Very long eye relief allowed mounting ahead of bolt handle. A very fine scope.