Downtube marks for the Lieberkuhn position. A Lieberkuhn is a parabolic mirror that fits over the down tube. Its role is to reflect light onto an opaque sample.
Lenses of microscope No. 233.
A: Eyelens
B: Field lens
C: Objective.
Separation distances are:
A-B= 7.0cm
B-C=12.5cm
This microscope has the typical three-lens optical system. The lenses are all simple and biconvex. The downtube is marked crudely with Lieberkuhn positions.
Interestingly, the downtube body is unusually thick-walled (3mm); especially when compared to typical Cuff-type microscopes of the era.
