The microscope body screws into the cantilevered support arm by threads on the outside of the objective.
Focus is by Rack & Pinion. The threaded rack is machined into the support pillar.
The microscope assembly screws into a threaded hole in the top of the storage case. The round piece at the bottom of the pillar is decoration only. It is not a compass joint.
The substage mirror attaches to the support pillar using a small-diameter pin (arrow). The mirror is 3.2cm in diameter. One side if flat and the other convex.