Kriegsmarine U-Boat 20mm Anti-Aircraft Gun Sight

Kriegsmarine U-Boat 20mm Anti-Aircraft Gun Sight. This is a gun sight for the 2cm Flak (Flugabwehrkanone) Anti-Aircraft guns mounted on German U-boats. These heavy duty optics were originally water tight, so they did not need to be removed before emergency dives. They could withstand up to 30 atmospheres at a depth of 300 meters. The optics are maker marked with 'bmk' indicating production by 'Srb & Stys' from Prague (Czechoslovakia) and marked with the unique serial number '138472'. The optics are clear and complete with reticle (Strichplatte). The sun filter, engaged with the lever in the centerTposition, is still present and functional. The often missing original rubber eyepiece is still present and flips down correctly. The rubber is still supple and has the correct drainage holes that would allow water to get out quickly. Rare and decorative original U-Boat 20mm Anti-Aircraft Gun Sight in good used condition!