This tractor has a shuttle shift it was called a "midship housing." The tractor has 5 forward gears and one reverse but with the shuttle shift it will go either way in any gear by shifting a lever to change direction. This gives you 6 speeds to chose from in either direction. The speeds are the same for forward and reverse. That's right it will go as fast backwards as forwards.
Unfortunately I don't know any more than this about this tractor. It has been severely cobbled. I need information on it, so if you can help please e-mail me. Thanks.