Drum Microscope, by G. Oberhaeuser, Paris

The stage plate has four pinholes to take stage accessories. Below the stage is an aperture disc that protrudes though a slit at the side of the instrument allowing it to be turned, and a plano-concave mirror. The base is a heavy brass plate weighted with lead and lined on the lower part with thick felt.

The upper part (stage and body) rotate on a heavy cylindrical drum. The brass body tube is adjusted by sliding it within a brass collar mounted on a heavy arm attaching it to the pillar. The fine focus is by a mill-edged screw at the top of the pillar.