3-3/8x7" card used by optometrists during the 1930s in the diagnosis of eye problems or to be used in a self-administered program to improve one's own visual acuity. The two images of Babe about to swing the bat and of a man jumping from a rock each have horizontal and vertical white line markers which when seen overlapping as a plus sign would determine a lens specification. "The Keystone Eye Comfort And Depth Perception Series" text on reverse side along w/Keystone View Co. copyright. Card is slightly curled w/age, o/w Exc. Unusual Ruth item.