A very rare 2.5 power Zeiss sighting system developed as a light gathering aid in low light situations. A special front sight attachment with a white pyramid to be used as the aiming point was clamped over the front sight of the rifle because the sight had no reticle, only a bifocal lens so the front sight would be clearly visible. See "The German Sniper 1914-1945 by Peter R. Senich, pages 57-61.