stereoview
Betts Fusion Test 2D; Slide DB-4D (Keystone #35097)
Betts Fusion Test 2D; Slide DB-4D (Diameter of Balls, 6mm)
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."
Wonderfully bold and modern; 3.5 X 7 inches. Housed in mylar sleeve for safekeeping.
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