This is a German stereoscopic rangefinder ( lenght 1 meter or 39.37 inch )
Range: 500 to 10.000 meters
Weight: 7 kg
These range finders were often used by anti-aircraft units, but also by the Artillery.
This one was made by FWQ, what stands for Saalfelder Apparatebau GmbH, Saalfeld
The rubber eye cup is marked "CXN" = Emil Busch AG Rathenow
It can be used as a binocular, but also as a rangefinder