OFF ON (embossed either side of the light switch) scale from 0 to 20 in increments of 1 (incl. 0.5 and 1.5) (embossed in white clockwise around the middle dial) scale from 0.5 to 12 in increments of 1 (incl. 0.5 and 1.5) (embossed in red anticlockwise around the middle dial) .5 20 X and 30 _ 10 (embossed beside the four leses on the top dial) W (scratched by hand between the top and middle dials) When the battery is exhausted remove at once to avoid corrosion of the handle. (printed in red on a small paper sticker inside the case) MANU 2nd quarter of 20th century This ophthalmoscope disassembles into two - the handle, containing the battery, and the eyepiece. They are attached by means of a small bolt which also allows connection of the bulb with the battery. Also icluded in the case is a spare bulb. This instrument was used to illuminate the interior of the eyeball and rendring it visible throught the pupil. Light is reflected from the mirror into the eye and the observer inspects through a small hole in the centre of the mirror furnished with changeable lenses.