Signedon circular nameplate above eyepieces: blc / EM0.9mR / 278287
on barrel: hSJ bLC EM 0.9 WR 278 287
FunctionA rangefinder is a device for determining the exact distance from the instrument to an object far away. This particular one is a German Army portable viewfinder for use by artillery units in determining the distance to their targets.
It works with the images coming from two telescopes that are looking at the same object but separated from each other a certain distance, in this case 0.9 meters. When looking through the eyepieces, the operator's brain will merge the two images into one image with a magnified perception of depth. At some point in the light's path before the eyepieces are reticles with identical geometrical patterns and at a set angle to each other such that the user can also superimpose them into one depth-enhanced picture.
In order to determine the distance to an object, the operator adjusts the angle of a lens at the end of one of the pipes until both the reticle image and the target image appear to be at the same distance (none is doubled). The reading in the adjusting know will give the distance to the target.
Historical AttributesProbably used experimentally by US Army.