Among the surviving accessories are four objectives numbered 0, 4, 7, and 9,
three eyepieces, an aperture stop holder with several stops, an eyepiece goniometer with
analyzing prism, the Bertrand lens and analyzer each mounted within the tube, the sub-stage polarizing
condenser system with iris diaphragm, and an object marker with a diamond tip
that is stored in its own leather case. A magnification chart is attached to the door of the case.
This microscope is an example of the Fuess Model III made in 1895. It is made
entirely of brass with bright lacquered, black enameled, and nickel plated
surface finishes. The main focus adjustment is by rack and pinion, while
fine-adjustment is by calibrated micrometer screw with verier located at
the back of the limb, which allows the measurement of the thickness of the object being observed. The end of the body-tube has a centering adjustment.
To facilitate the change of objectives, the latter are not screwed on, but
held by the clamp. Immediately above the clamp is a cavity for the introduction
of a Klein’s plate, quarter-wave plate, etc.
The stand measures about 15.5-inches
tall inclined as shown in some of the photos. The rotating stage is divided
into 360º, with two verniers each reading to 5 minutes. The stage has centering adjustments and is
provided with cross-divisions for the orientation of the preparation.
The sub-stage, which focuses by rack and pinion, holds a polarizer having
an iris adjustment to modify the light and a three element condenser. The
top elements can be moved aside for low power work using a lever mounted
on the side of the stage. The substage can also mount an aperture stop
holder for use of the microscope with ordinary light. The analyzing prism
is mounted on a slide within the tube. Alternatively, the analyzing prism
within the tube can be slid out of the optical path and replaced with a
different analyzing prism that is located above the eyepiece in a goniometer
attachment. A Bertrand lens can be mounted within the tube which can be
focused manually by moving the nickel-plated draw tube. The mirror is mounted
on an arm which is moveable side to side.
Elsewhere in this collection is an example of the earlier form of the model III
and a later example of the Model IIIa. The Model IIIa differs from the Model III mainly in
the use of a wider tube taking a 30 mm ocular.