A fine example of an optometer in brass, ebonised wood and steel, made by and marked F A Hardy & Co Opticians Chicago Illanois. Patented 29th April 1902.
The eyepiece is held to one eye and the brass screw on the main stem is turned until the disc comes into clear focus. This measures the correction required for reading glasses. Has a rare brass eye shield for the untested eye. Built to a very high standard and in perfect working order 100 years later.