Versatility ....

You can even use regular 35mm slide film to make 35mm full frame split stereo slides, just like the beam splitters of the 1950s and 1960s made, the 321 Camera makes the images each with a separate lens just like the very expensive two lens adapters of the 1950s, made by Leica, Nikon, Exakta, and Kindar, which today cost thousands of dollars just to attach them to your regular 35mm camera.

Additionally you can make separate half/frame slide images to be mounted in standard 1-5/8" x 4" mounts such as RBTs to view in standard Realist format viewers.

The possibilities are plentiful with this ingeniously designed camera. And it's a fun camera to use.