"Drum" microscope

The ends of the tube house the eyepiece and lens. On one side is a screw that moves the tube toward or away from the sample using a gear, to enable coarse focusing. Just under the lens is a circular stage. It has a central hole with 2 plates and side openings between which the slide holding the sample is inserted. The stage has a small hole for a magnifying glass or other instrument to hold items in place for examination. Under the stage is a concave mirror used to reflect light through the optical axis. It is held at the sides by screws into the lower barrel, which help it move in a single direction. There is an inscription on the barrel with the name of the manufacturer: "Negretti & Zambra, London."

Henry Negretti (1818–79) and Joseph Zambra (1822–97) worked together in London making scientific and optical instruments. They also ran a photography studio. They were active right from the beginning of their partnership in 1850 and later even supplied the British royal household.