Betts Fusion Test 7B; Slide DB-5B (Keystone #35103)
Betts Fusion Test 7B; Slide DB-5B (Diameter of Balls, 2mm)
Stereo card from Keystone View Co.’s stereoscopic Betts Fusion Tests, ca. 1940. Slide DB, showing an increasing diameter of colored balls. Betts Telebinocular Tests were commonly used by schools as a screening device for vision dysfunction, much to the chagrin of the American Medical Association, which found the test over-diagnosed vision impairment and deemed it "unacceptable."
Card slightly bowed, otherwise VG; 3.5 X 7 inches. Housed in mylar sleeve for safekeeping.