This is the camera my dad would use to create his double, triple, or quadruple exposures. Here's a picture of him posing with his friends, (on the right) when he was a young man. He probably set this up and took the picture with whatever camera he owned at that time. The following pictures are a series of his multiple exposures. Yes, he was a little nutty. I don't have a scanner, so took a picture of these, but they really are much clearer than this.
Watercolor, 7"x 7"