Editing Periscope (section)

===Gundlach and Vickers 360-degree periscopes===
An important development, the [[Rudolf Gundlach|Gundlach rotary periscope]], incorporated a rotating top with a selectable additional prism which reversed the view.  This allowed a tank commander to obtain a 360-degree field of view without moving his seat, including rear vision by engaging the extra prism.  This design, patented by [[Rudolf Gundlach]] in 1936, first saw use in the [[Polish Army|Polish]] [[7-TP]] light tank (produced from 1935 to 1939).

As a part of Polish–British pre-[[World War II]] military cooperation, the patent was sold to Vickers-Armstrong where it saw further development for use in [[British Army|British]] tanks, including the [[Crusader tank|Crusader]], [[Churchill tank|Churchill]], [[Valentine tank|Valentine]], and ''[[Cromwell tank|Cromwell]]'' models as the [[Vickers Tank Periscope MK.IV]].

The Gundlach-Vickers technology was shared with the [[United States Army|American Army]] for use in its tanks including the [[M4 Sherman|Sherman]], built to meet joint British and US requirements. This saw post-war controversy through legal action: "After the Second World War and a long court battle, in 1947 he, Rudolf Gundlach, received a large payment for his periscope patent from some of its producers."<ref name=r1/>

The [[Red Army|USSR]] also copied the design and used it extensively in its tanks, including the [[T-34]] and [[T-70]].  The copies were based on Lend-Lease British vehicles, and many parts remain interchangeable.  [[Wehrmacht|Germany]] also made and used copies.<ref name=r1>Łukomski, Grzegorz and Stolarski, Rafał E. (1999) ''Nie tylko Enigma... Mjr Rudolf Gundlach (1892–1957) i jego wynalazek'' (Not Only Enigma... Major Rudolf Gundlach (1892–1957) and His Invention), Warsaw-London.</ref>