This particular example
is fully equipped for observations using reflected or
transmitted polarized light. Note that the Bertrand
lens, which has a built in mechanism for focusing,
can be screwed onto the 8X eyepiece. Special low
power oil immersion objectives are supplied. The
objectives are corrected for a 215 mm tube length. In
use, the draw-tube should be set to zero (fully
extended).
The following was taken
from the 1929 Leitz Catalog of Microscopes: