The focus mechanism consists of a long threaded rod that is screwed into the specimen holder support shaft (A). Turning the thumbscrew (arrow) moves the base-plate (B), and specimen closer or further from the objective. The specimen holder base-plate dovetails into its support plate.
Specimen height can be set by turning the rack & pinion mechanism (A) with the long control rod.
Specimen translation is controlled by a lateral rack & pinion mechanism (B) actuated by the same long control rod.
Control rod for setting sample height and lateral position.