James,
Do remember what the adjustment mechanism on the disk looked like? As I remember, ours had a 2" pipe with holes in the top that ran from the rear disk to the front disk. The front disk had a arm with about a 2" protrusion that would go into the holes in the 2" pipe when the tractor operator pulled the rope attached to the arm. The arm moved down and had a spring attached to it so when the tractor backed up it pulled the protusion out of the hole so you could either move forward or backward and pull the rope when the disk was in the position you wanted.
Hope this description makes sense.
Thanks.
Jim