The early 4630 Quick-Coupler was convertible from Cat3 to Cat2, and the top hook was a part of the cross bar. The anchor point on the tractor had two positions for the top link to maintain the correct geometry for the three point linkage. 4520, 4620, 5010 and 5020 tractors all shared this design. All of these tractors came standard with that style coupler if ordered with a three point hitch. Late 4630 tractors got a new design coupler that converted to Cat3N if needed, from the factory assembled Cat3 setting. This design used the bolt on top hook and the tractor had a one position anchor point. The late model design were used by the tens of thousands and are easily found used. Hope this helps.