The rectangular part in your pics is a production cross slide. It makes it easy to put a tool on the front and backside of the lathe. It is easy to change from the standard cross slide to the production slide. Many people say production slides are less apt to chatter then the standard compound slide. I started machining in 1953 with a new Logan that was set up with the production slide. And I still prefer it to the standard slide. I didn’t see the gib for the production slide in the pic.