Guess if you can... I am tempted to ask Charles not to play along as he ALWAYS figures it out first, but it is Christmas time so I am going to be lenient
Water bubbles (or droplets) at the limit of the water/air in a drying microscope slide. Some bubbles walls act as mini Bertrand lenses imaging the pol interference cross.
I'm looking for the the extemely rare V-IM magnification changer for the E800 scope. If you have seen a listing or have one for sale please let me know.