The Hevelius focus screw is fixed at the top of the rectangular microscope body support pillar (left). As the thumbscrew is turned, the microscope body is pulled up or pushed down. A spring (above) maintains pressure against the support shaft and increases stability of the microscope body.
The main support pillar (7x7mm) attaches to, and the focusing screw passes through the brass stage insert.
Brass focusing knob.
This brass nut screws onto the threaded pillar end and fixes the support pillar to the stage.