I don't know why the picture rotated when I uploaded it.
The whole piece rotates in the tube part of the stand and has a locking screw. The plate on top rotates when the handle that is missing a knob relases a pin, and there are 8 locking positions. The plate has tapped holes.
The wheel moves the flat surface from a vertical position, but does not allow it to go completely horizontal. It is as far horizontal in the photo as it will go.
Picked this up today with some other tools, but have no idea what it goes to. I figure it is some type of machining fixture. Any help would be appreciated.