Ernemann manufactured different stereoscopes to support it's stereo camera portfolio: hand-held stereoscopes for different glass formats, a chain-type viewer and a slide-tray cabinet viewer. The Ernemann Universal Stereoscope is a wooden foldable viewer that supports formats 45x107mm up to 8,5x17cm. It must have been a useful device for retailers and photographers who had to deal with different image types and formats.Unfolded, it consists of two parts that are mounted on a base plate. The front panel contains the lenses. While focusing, the whole front panel moves forward or backward. The distance between the lenses is adjustable and the set distance is visible in millimetres. The rear part consists of a frosted glass where the stereoviews are placed. Behind the glass, a folding white flap provides a neutral background while viewing the stereoviews.
This compact and versatile stereo viewer has its disadvantages. It's an open system so it's prone to reflections and it lacks the intimate viewing experience of a closed hand-held stereoscope. Another drawback is the small focus knob, which is partly built into the base plate. It contributes to the compact size of the viewer, but it makes focusing more difficult. Finally, the stereoviews should be placed behind a metal clip. Placing is cumbersome and you have to be careful to not scratch the stereoviews.
So this device may not be the most user-friendly stereo viewer, but its unique design makes it a cherished part of my collection.