Disassembled optical body tube consists of three sections: Lower objective tube, middle field lens tube, and the eyepiece section.
A: objective, B: field lens, C: eye lens.
Objective #"5" has a single biconvex lens mounted at the end of this brass body. The body has internal threads to attach to the downtube. It also has exterior threads, possibly for a Lieberkuhn.
Lommers compound microscope optics
Typical three-lens optical system:
A: objective dia=0.6cm, f=2mm
B: field lens, dia=3.2cm, f=8.5cm
C: eye lens, dia=2.7cm, f=3.3cm

All lenses are biconvex.

The microscope body is 19cm in length.