Compound Drum Microscope and Eyepiece, by Varley, London, Mid 19th Century

A copper alloy cylinder stands on a larger copper alloy ring. A slot is cut out of the cylinder to allow light to the concave mirror. There is a white disk on the reverse of the mirror and a mill-edged knob on the side of the instrument adjusts the angle of the mirror. At the top of the cylinder is the circular stage with a recessed stage hole. A copper alloy disk, with a pinhole at its centre, on top of a tube fits into the stage hole. There is an aperture at the lower end of this tube. A shaped limb, screwed to the stage, carries the body tube on a rack and pinion. A knob on the limb moves the body for focusing. The eyepiece has a lens set in a blackened disk on a tube and a second lens at the other end of the tube.  This pushes into the top of the body. There is an external thread at the lower end of the body for objectives.