Mackenstein’s Stéréoscope-Classeur Portatif is a compact and rare stereoscope. It is probably the most compact tray-based stereoscope with an advanced mechanism ever designed. Most stereoscopes use a rail on which the slide tray moves to a position where a fixed positioned metal finger lifts a slide and places it in front of the lenses.
When operating the Stéréoscope-Classeur Portatif, the tray remains in place. There are 25 curved fingers with grooved edges positioned under the tray, one for each slide. The panel with the lenses can slide out of the housing by turning a knob on the right side of the device. A trigger arm is attached to this moving panel. Depending on its position, one of the fingers is triggered by pressing a button on the top right of the device. The finger picks up the slide from the tray and places it in front of the lenses. Releasing the button places the slide back in the tray.
Pressing a small plunger on the front panel swings a shutter away from the centre of the slide, and reveals any written descriptions that are applied to the slide. The wooden housing is made of mahogany and optional storage cabinets for storing slide trays were available. The extreme rarity of this stereoscope suggests that the design, with its exotic mechanism, was not a commercial success.
| Manufacturer: | Mackenstein |
| Year of introduction: | 1911 |
| Type: | Table-top |
| Viewer: | Multiple-view |
| Mechanism: | Tray-based |
| Stereoview support: | Glass |
| Format: | 45 x 107 mm |
| Number of slides: | 25 |
| Lens focussing: | Yes |
| Inter-ocular adjustment: | No |
This also moves the lifting mechanism, allowing it to select a slide in the slide tray.