The focus mechanism consists of a rack & pinion coarse focus (A) and a screw thread/spring fine focus (B).
The single objective is the typical ganged French style. The middle optic is engraved "1", the top is "2". Lens "3" is missing.
Coarse focus rack & pinion
The wooden base has these nail holes.
The objective mounts to the body via this bayonette mount.
Top view of the microscope body showing the bayonette mount. Note that the eyepiece optic is missing.