Used at the First Gymnasium of Athens, in Plaka.
"The solar microscope is in reality a magic lantern illuminated by the sun's rays; it serves to produce highly magnified images of very small objects. It is worked in a dark room"
Ref: http://physics.kenyon.edu/EarlyApparatus/Optics/Solar_Microscope/Solar_M...

The apparatus is probably made by Krüss company.

Probably made by Duboscq

It consists of a clock mechanism with a frame for a mirror.
The mirror is missing.

Functioning:
The mirror reflects the sunlight providing thus a light source for optics experiments. The clock mechanism follows the movement of the sun in order to keep the reflection focused.

Plain mirror part of a heliostat.

Functioning:
The mirror was used to reflect sunlight for experiments in optics.

A device similar to the ordinary spectrophotometer but containing particular modifications to provide for the comparison of two sources