In the early 1970s, Nikon designed the inverted microscope Model MS to serve as a sister instrument to their upright Model M compound microscope. Equipped with two transformers, the Nikon MS can employ simultaneous diascopic and episcopic illumination.
The instrument features a monocular viewing tube and a photographic tube that emerges from the side of the microscope's mirror housing. The standard condenser unit of the microscope includes a built-in aperture diaphragm, but an optional, long-focus condenser may be alternatively utilized. Mounted on a central post above the condenser unit and circular, rotating stage is a removable dia-illuminator. For polarized light and phase contrast microscopy, various analyzers, polarizers, and filters may be used in conjunction with the instrument. Microscopists utilizing the MS may also choose between individual phase-contrast annular diaphragms or a four-way turret to match the 10x, 20x, 40x, or 100x objective.