[Taxacom] Instructions for a polarizing unit for an AO Spencer Stereo Microscope

[Robin Leech]

Hi Taxacomers,

I recently purchased an AO Spencer Stereo Microscope,
Model 25L, made about 1955 or so.

A polarizing unit came with it, but no instructions.
Does anyone know where I might find the instructions 
for the polarizing unit?  

I intend to study polarizing receptors in the Posterior 
Median Eyes (PME) of spiders, and may be using 
both transmitted and reflected light.

Any help much appreciated.

Robin