Snellen Vision Testing Cards Set for Railway, Marine and School Exams, Early 20th C. name tags I'd guess 1940s-50s c

I'd guess 1940s-50s c

) Nicely graphic in red

but it's clearly got age to it

Plus a great

but completely blank back

Snellen Vision Testing Cards Set for Railway, Marine and School Exams, Early 20th C. name tags I'd guess 1940s-50s cFound in their original envelop, with Millar and Wel_ (?) Opticians on, Boston stickeron the face and instruction card still inside, this appears to be a complete, or nearly so, set of early 20th c. Snellen vision testing cards. Nineteen cards total, plus instruction card, with three of the cards showing railway signals to be read at a distance of 20 feet as these were commonly used for testing the vision of train conductors railway workers. Included: