These 7/8" x 1/2" glass dolls' eyes were made prior to 1912. They are flat-backed, and come as two separate pieces: the sclera (the white part) and the iris. (Technically speaking, our glass iris includes the cornea as well). The iris is clear, or may contain traces of paint from its days in the factory as it waited to become a doll's eye. It is up to you to paint the pupil (presumably black) and the iris (whatever color suits your fancy). When you receive the doll's eye, you might be inclined to think that these two pieces don't look like much (as it were), but once you color them and join them with a tiny dab of glue, the eye will come to life. (Only figuratively, of course.)
These doll's eyes were manufactured by Leo Popper & Sons of Brooklyn, N.Y. The company manufactured many unusual glass items like elevator buttons, railroad warning light lenses, and hatpin heads. They also provided the glass for the Statue of Liberty's torch after it was damaged by the explosion of a munitions ship in New York Harbor in World War I (http://en.wikipedia.org/wiki/Black_Tom_explosion).
Mr. Ferguson of Roanoke writes "I used to have a problem with solitary drinking. Now I stick one of your dolls' eyes into one of my olives in place of the pimento, and drop it into my Martini. This way I don't feel so alone."