This is an optical range finder that works from 8 to 100 feet.  By rotating the distance knob until the two images are aligned the range can be read on the knob.  Construction is cast and machined aluminum with glass optical elements.  A 4 foot long lanyard allows the instrument to be carried around the neck, or in it's leather case that has a belt loop on the back side.  The two viewing windows on this unit are 6 inches apart.  Military range finders have the windows much farther apart to read longer ranges.  Cameras, like the Lieca, have the windows closer together and measure shorter ranges.

The label reads:
EDSCORP
Field Range Finder
Edmund Scientific Co. Barrington, N.J.
Pat 2627779 Made in the U.S.

Class 356 is for "Optics: Measuring and Testing" and sub class 17 is for "Base line instrument (i.e., base is a part of instrument) + Image displaced by rotating reflecting element".  Search all 356/17 patents.

The cited patent is:
2627779 Range Finder Feb. 10, 1953 by Stanley. S. Szelwach assigned to Q.O.S. corp. NY.
Reference Patents
2186806 Range Finder Jan. 9, 1940 by Oscar. Liebmann assigned to Q.O.S. corp. NY
2058484 Base Type Range Finder Oct. 27, 1936 by Joseph Mihalyi assigned to Kodak Company, N.J.  The patent figures show a range of 3 to 100 feet, but the base line distance only appears to be a couple of inches.  The distance scale can be read through the eyepiece.