What is this ?

[Plasmid]

I recently purchased a Microstar that came with a teaching adaptor and two heads, my question is... What is that box that sits below the head and attachment? And what is it for?

[dtsh]

Does it have a lever on the other side with a rotatable knob? It looks like the bertrand lens / aperture viewing unit.

[apochronaut]

It's a pointer, used as a teaching aid with a teaching bridge.

[PeteM]

The one right above the stand (about 5/8" thick) may contain a polarizer. Nice accessory to have. I have about a half dozen marked "1991" on "Micronaut" socpes that have a rotating knob that moves between an open position and an analyzer/polarizer. Add a polarizer above the field lens and you have a basic polarizing scope.

As DTSH said, AO/Reichert also made similar intermediate pieces with a Bertrand lens, but I don't think this will be one of them unless you also have phase objectives and a phase condenser on the scope. Those intermediate pieces will be marked "1204."

Apo has it right on the upper teaching adapter with a pointer located inside. Yours looks to be missing the lamp? If so, a tiny LED flashlight could be added.

Can't see if you got a trinocular head, but your teaching head could be configured as a 50-50 split with half the light going to eyepieces and the other half adapted to a camera. Could be useful, say, for a teacher hoping to chase a specimen through the eyepieces while displaying a video on a large screen.

[apochronaut]

There were 3 thin square accessories that could go into the infinity space : the two mentioned plus a plain distance piece. The anayzer and distance piece are the same depth. You most likely have the analyzer. It has a thin black rotary wheel on it.
The Bertrand lens is much thicker, almost double the thickness of that piece.