Tray-Stereoscope ‘Métascope Spécial’ together with Original Owner’s Photo Collection

To place a slide tray, the lid on the top and the front pan­el must be opened. The lever that loads the slides is in the down posi­tion and locked. After the slide tray is insert­ed, the lever is unlocked and moves upward. The first stere­oview is posi­tioned in front of the lens­es. The slides are dis­played one by one by push­ing the lever down repeat­ed­ly. An indi­ca­tor on the right side of the device shows which slide is loaded. With the lever in the locked posi­tion, the indi­ca­tor can also be used to quick­ly nav­i­gate to a spe­cif­ic image.
(from: Com­pendi­um of Stereoscopes)

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