Tray-Stereoscope, special focus feature

The wood­en trays con­tain 25 slides each and can be insert­ed into the view­er by flip­ping back its top. Then, by turn­ing a crank on the right side of the hous­ing, one slide after anoth­er can be exam­ined. Each half-turn of the crank advances or returns the slides and moves the tray for­ward. A knob on the front serves for focussing by mov­ing the entire view­ing mech­a­nism inside the hous­ing back and forth.
This view­er seems to be an unique piece of his­to­ry, though close­ly con­nect­ed to the ‘Hemdé’ view­ers which are already among the rar­er tray-stereoscopes.

Fur­ther read­ing: Stere­oscopy His­to­ry Series — Hemdé (A. Ruiter)