The gimbal illumination mirror is mounted to the lower support.
An aperture wheel is mounted under the stage. The apertures control the contrast of the sample (to a small degree).
The aperture wheel has four openings of 3, 6, 9, and 12mm diameter. The three brass tubes are mounts for the stage clips and Bull's-eye lens.
The Bull's-eye lens is used for epi-illumination of opaque samples. Dia=35mm, f=65mm.