That my friend is a copy of a Leica Focaslide close-up attachment for a Barnack.
Once the camera is mounted to the Focaslide, the entire apparatus needs to mounted to either an enlarger or copy stand. With the proper extension tubes, one can either do macro work or copy work, such as photographing pages of a book.
It's awkward in use - but it did get the job done in the pre-Visoflex days, so long as it was mounted to a firm post.