Epi-illumination is where the specimen is illuminated from same side as objective. This allows non-transparent specimens to be viewed. The Zeiss IM microscope is capable of doing this with right bits. Trying it today (photos below) show that I am missing, by the looks of it, an insert for the housing under the objective turret which redirects light up into the objective……another wait for one to cone up on ebay ahead.
Photos below show illuminator in epi-illumination position, housing below objective turret, and on-site this housing showing light coming through from illuminator in epi-illumination position.