Vickers Tank Periscope MK.IV

The Gundlach Periscope, usually known under its British designation as Vickers Tank Periscope MK.IV, was a revolutionary invention by Polish engineer Rudolf Gundlach, manufactured for Polish 7TP tanks from the end of 1935 and patented in 1936 as the Peryskop obrotowy Gundlacha.

By rotating the periscope and allowing the tank commander to look backwards through the second eyepiece, he no longer had to change position to look behind the turret.

Early tanks had small turrets and fixed seating, without an independently rotating cupola, and so the commander wasn't easily able to move himself to another rear-facing periscope.

As a part of Polish-British pre-war military cooperation, the patent was sold for one zloty to Vickers-Armstrong.

After the fall of Poland, Germany, USSR and Romania captured some equipment, allowing them to copy the invention.