Leitz microscope #188 focusing mechanisms

This microscope has separate coarse and fine focus controls.
Coarse (A) is a typical rack-and-pinion that moves the body tube.

Fine focus (B) consists of a spring-loaded vertical column actuated by a fine-pitch screw thread.

Coarse (A) and fine (B) focus mechanisms
Fine focus control knob (inverted)
Fine focus control is graduated in 10µm increments
Fine focus control screws into shaft at "A". When turned hardened steel point (control, above) presses against a spring-loaded triangular shaft (B). This moves the microscope body support arm (including the coarse focus rack-and-pinion).