The Oppelt microscope has four lenses:

A: Objective: dia=1.5cm, f=1.5cm;
B/C: Two lenses within the intermediate tube
D: Eyepiece lens: dia=2.6cm, f=2.5cm

Intermediate tube consisting of two lenses, each 3.5cm diameter, set in a two-piece wooden frame. The entire assembly screws into the top of the microscope body tube.
Intermediate lens tube acts as a single Field lens