Vintage Abrams Stereoscope

An old Abrams Instruments Corp. stereoscope made in the US. From its appearance it matches those built in the 1940s to mid 1950s but I cannot be sure; they were often used to look at overlapping pictures that were taken in the air. Closed they are 4 5/8" wide, 2 1/8" tall and 3/8" deep. For shipping the 2 metal side frames will be detached. There is a serial or inventory number that has been scratched onto its left side.