It looks like the disk was made from a larger pull type unit.
Perhaps at one time it was a 'Fast Hitch' style for an IHC tractor (their answer to the 3pt in the 1950's). If so, then that wheel would be the fore/aft leveler - extend th shaft to lower the rear, shorten to raise it. It is important a 3pt disk is level. The 'Fast Hitch' had no top link, so this type of leveling was needed.
If there is no give or hinge in the 3pt parts welded on now, then it is only a brace now, & the wheel is just along for the ride.
--->Paul