So, one could take an old stereoscopic photo card and scan each image then create an animated gif in Photoshop that tweens the two images as a loops and voila?
Yeah ... I think if the scans are done at two slightly different angles, it could work. The two images are then created into a .gif image.
Here is some more info on Wiki (called wiggle stereoscopy) ...
http://en.wikipedia.org/wiki/Wiggle_stereoscopy