Stadimeter Mark III in Leather Case, US Navy
This is an original WWII-era Stadimeter Mark III as used aboard ships of the US Navy.
A stadimeter is a rangefinder, used to determine the distance from the user to an observed known target. By viewing the target through the device and turning the knob until the presumed height of the known target is bracketed between the upper and lower limiters in the viewfinder, one can then read the distance of that target on the corresponding height on the side dial.
The device is in fine condition given its age, and functions as it should. Measures ~ 7 in x 5 in x 2 in.