Joking aside, it's called a Focalslide. You mount camera on the slide (different models for LTM & M). Then mount it to a copying easel. Much like the Visolflex, you could mount different lenses, or the head of certain lenses, or the collapsed position of the Elmars and Summircons using various adpaters, The ground glass is missing the eyepiece (a tube with diopters). But you mounted your camera, then the lens and adapter, and move the whole thing up & down until your subject is in focus on the ground glass. The you slide the camera horizontally to replace the ground glass and take the picture.
It was used primarily for document copying (in my experience) because once focused you could just change the pages and snap away.
I suppose people don't know what microfiche is?
