This periscope was used during WW2 extensively made for armoured vehicles.Minneapolis-Honeywell was approached by the US military for engineering and manufacturing projects. In 1941, Minneapolis-Honeywell developed this superior tank periscope and camera stabilizers, as well as the C-1 autopilot.Rectangular periscope with screw & clip device to hold in position, painted olive drab.On one label: PERISCOPE M6/ MINNEAPOLIS HONEYWELL REGULATOR COMPANY/ No 4XO/ 1943. On paper label: Periscope Adjustments Knob Settings (indecipherable). On one side handmade scribbling unable to analyse: PVNCAN/HARE/838 4551periscope, armoured vehicles, tanks, ww2, us army, chaffee, stuart, shermann, minneapolis