Microscope No. 213 has only this one objective. It is marked "1" and
"Ernst Leitz Wetzlar".
Lens No. 1 is a 3.2x objective with a focal length of 40mm. It consists of two lenses:

Front lens: dia=9mm, f=5.5cm
Back lens:dia=9mm, f=6.5cm

Lenses for petrographical microscopes were often strain-free to decrease intrinsic birefringence of lens elements.

This image shows the Leitz objective changing and centering device—the "Objective Clutch".
This collar was screwed to the objective to act as the mount for the quick-change clutch.