Seton Rochwite designed the Stereo Realist camera between 1943 and 1947 for the David White Company. Seton Rochwite Instruments subseqently designed an attachment for the Realist that allowed for three coupled polarisers to be added to the camera - one for each lens, and one for the viewfinder. A very limited number were produced. An astounding feature of the design is that the polariser attachment replaces the original lens cover on the Realist, while at the same time fitting within the Eveready case, whith-out losing any of the functions of the original lens cover.
A black-anodised flap (that is hinged at the top, and engraved with the logo of Seton Rochwite Instruments), can be lifted up revealing the three polarisers in place over the lenses. If the polarisers are not required, they can also lifted up and the camera used as normal (as shown in the photo).
The polarisers are linked via a common connecting rod which attaches to each polarsier at the perimeter via a pin. This allows for a total rotation of the polarisers of 90 degrees, and can cater with polarising angles encoutered in outdoor scenes. Exposure determination would be by allowing for a given loss (of say 1.5 stops) through the polarsier, as it doesn't appear praticable to meter through-the-polariser.