Good point about focussing. The Zeiss west microscopes had a relay lens transmitting the projection ocular rays to a device that had a separate matte screen for fosussing (and in the more recent varieties, an electonically controlled shutter (prontor magnetic) in the 47-60-12-9901 tubus. They also used a motorized yashica camera for that.

The only unsolved question i have about my microscope Contarex is that the "schwalbering" is larger than that of both that of the west microscopes and of my Tessovar

p.