Quote - Holy scary machines batman!  I'm not sure I want one of those near my face!

Trust me, no one did but that's what was used from somewhere around 1875 when the electric drill was invented to replace the foot treadle one until the early 60s when air/water ones came into use.  Even so, the electric ones continued in service for things like cleaning at elast into the late 80s and I wouldn't doubt a few are still in use for that.

Quote - Hmm...  I'm not the best modeler around but I might take a crack at this.  Though I do have a backlog I looking in here for future projects.  Hopefully someone else will beat me to this so you can get it sooner! :)

I'd greatly appreciate it.  It's going into a 1930s medical center so the third one wouldn't work however it helps show how they were assembled.  Kind of.

Something that's not obvious is that the pulley thingies aren't actually attached to the arms but rather are free to swivel as the arms are moved around.  This allows a tremendous freedom of movement to the handpiece.  Also, on some the motor moves with the first arm rather than has a set of pulleys between it and the arm.  In both cases, it's free to rotate on a pin through the base. 

If any other questions come up, I'll try to answer them.  I'm also looking for one IRL to attach to a watchmaker's lathe for detail work.  If I find one before anyone starts a model (not really likely but I can hope), I'll be able to take detailed photos to help with modeling it.