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This original Keystone Diagnostic Series DC-51 stereometric eye-training card was used in aviator visual-acuity and depth-perception testing. Produced by Keystone Stereoscopic Service, this card features paired airplane images and vertical letter strips designed for use in specialized stereoscopic viewers. These cards were part of professional aviation vision-training sets used to assess clarity, depth judgment, and reaction to forward-projecting letters.
The card displays bold aircraft artwork and six columns of letter panels used for visual-acuity calibration. A great collectible for aviation enthusiasts, optometry collectors, and owners of Keystone training sets.
Condition:
Very good vintage condition with light edge wear and minor surface marks typical of handled stereoview diagnostic cards.
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