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 since end of 1935 and patented in 1936 as Gundlach Peryskop obrotowy. It was the first device to allow the tank commander to have a 360-degree view from his turret with a single periscope. 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.