Stereo Lens Adapters (1939 and 1971)

Some ideas hang on forever. This Stereo-Tach lens attachment from 1939 antedated the half-frame Stereo Realist by several years, but never caught on. Interesting idea—you screw this onto your lens and it splits the frame into two half-frames, each with a stereo pair courtesy of the mirrors that offset the point-of-view. Leica made an attachement for their cameras (I'll scan it when I find it again). You could either print the pair, cut them apart and mount them on a card to fit a turn-of-the-century Holmes-style viewer, or I believe there was a hand-held viewer, again using mirrors to split the pair for proper viewing.

This Miidi advertisement is from 1971. I'm not 100% sure if the same attachment works on both the camera and the slide projector, or if you need two different ones. I am also assuming, as the copy doesn't say, that the lenses have polarizing filters set 90° apart so you can view the slides using polarizing glasses.

I wouldn't mind having this system, it would be fun to try it out; but so far I haven't been able to find any of it for sale.