Richard offered several projection units to convert Taxiphote viewers into projectors. Early styles were mono only. Later versions could project anaglyphic stereo. Anaglyph is the red/green process we all remember from the 3D Sports Illustrated Swimsuit Issue. I have no idea of the age of this unit. It is Richard Patents marked and has a three digit serial. It wasn't until after installing the unit on a Taxiphote I realized my photos were upside down.
It had to have been a difficult task to project viewable stereo pairs from a Taxiphote. Modern (meaning anything built after WWII) projectors have adjustments for rotation and convergence, and even with these image mounting is extremely important. Considering how the old glass slides were transposed, alignment errors had to be more the norm than exception. Small errors, which are barely visible in the cabinet, will become big headaches when projected.
Operation of this mono unit is extremely simple. Open the cabinet and remove the rear frosted glass. The light unit clips into the aperture and incorporates adjustment capabilities to fine tune location of the lens. The light from a 220v bulb is concentrated directly behind the slide, which must be reversed in the tray. By dramatically increasing the light behind the slide, it throws enough to become visible on a screen. If you stand back from a normal Taxiphote and look through the lenses, you will see a perfectly sharp, clear portion of the image. This is in effect a "projected" image.
I have not yet opened the light unit, but I'm sure a 110v bulb could be rigged for purposes of experimentation.