The Sawyer's Bi-Lens 35 is a classic example of mid-century "pseudo-stereo" technology. While it looks like a 3D viewer (similar to Sawyer's more famous View-Master), it is actually designed for standard 2D slides. By allowing the user to view a single slide with both eyes simultaneously, it creates a much more immersive experience with a perceived sense of depth. This unit is made of beautiful, dark chocolate brown Bakelite. It features an internal light source triggered by the large "PRESS" button on the top. This specific version is the deluxe lighted model; a rarer "natural light" version existed that required holding it up to a window. The bottom plate unscrews to reveal the battery compartment for the two C-cells that power the internal incandescent bulb.