Le Polyphote looks more like a common multiple view stereoscope than Bize's other designs Minimus and Multiphote, which are known for their simple mechanism. A 1910 advertisement lists the Polyphote as a new device, so I assume this is the year of its introduction. The device was available for 45 x 107mm and 6 x 13cm glass stereoviews.
The viewer uses a slide tray for 25 slides. What's special is that the tray is compatible with the Taxiphote trays. Perhaps Lucien Bize wanted to piggyback on the popularity of Jules Richard’s well-known stereoscope design and focused on this target group.
By turning a key-shaped knob anti-clockwise, a glass slide is lifted out of the tray and placed in front of the lenses. By turning clockwise, the slide is placed back in the tray and the tray is moved so the next slide can be loaded. With a button on the left it's possible to navigate to a specific slide in the tray. The mechanism used is relatively simple which makes it a compact device.
The lenses of the Polyphote can be focused and the distance between the lenses is adjustable. At the bottom of the device there is a compartment to store one tray. On the right side, a fold-out plate with a little mirror is probably intended to read the number on the tray. It suggests that the original slide trays of the Polyphote contain an index, but I'm not sure because my device is purchased with a Taxiphote tray.
Finally, I saw a model on the web of a Polyphote where the base plate of the viewer can be tilted to create an oblique viewing angle, which can improve the viewing experience.
- Lucien Bize advertisement from 1910