Pictured from my collection is an optical gunsight for a 3.7 cm anti-aircraft gun (Flak M42) manufactured for the Kriegsmarine. The code for this manufacture is 'dow' (Waffenwerke Brunn A.G. (1943 - Opticotechna Gmbh, Prerau Czech.)). The optic has a wide field of view with a ranging reticle. Even though designed to withstand harsh environments, this optic was made to be removed from the weapon system mounted on an U-boat .