Tonight I talked with my friend, Jim Moore (not the APUG member same name), about this slide show we put together back in college. Shot in both black and white and color and then duped onto (expired) copy film through pin registered 4x5 masks... I can't remember how we performed the double-exposure on dupe film. Our Pentax Spotmatic and OM-1 didn't do double-exposures properly. I think we borrowed a Nikon, but cannot think who had one.