The epi-illuminator converted the Model S microscope, built during the late 1960s, from a tool for studying translucent biological specimens into a tool for studying the surface of opaque specimens such as metals.
The illuminator is housed in an intermediate tube positioned above the revolving nosepiece and beneath the binocular eyetubes of the microscope, providing a uniformly bright viewfield at all magnifications. A half-reflecting mirror swings out of the illuminator body making it easy to change from episcopic to diascopic illumination.
Green, yellow, and daylight filters were provided with the illuminator and a polarizing attachment was available as an accessory. The epi-illuminator could be used with any of the eyepiece tubes available for the Model S microscope.
Interchangeable parts made the Model S microscope a versatile tool for studies in biology, medicine, and metallurgy. Depending on the user's needs, it could be equipped with various combinations of eyepieces, eyepiece tubes, objectives, condensers, and stages.