http://jamesdjulia.com/item/2668-391/

Germany was one of the first nations to really get into the sniping business during World War I, and this is an example of their sniper rifle of the period. The base rifle is a standard Gewehr 98 in 8mm Mauser. Optics form a multitude of different commercial manufacturers were used, mostly 3x and 4x in magnification. There was no specific military scope pattern. Unlike today's much more developed telescopic sights, this type had its windage adjustment built into the mount instead of the scope, and used a BDC (bullet drop compensator) elevation dial which moved the reticle up and down in the scope's field of view.

http://www.patreon.com/ForgottenWeapons