Here is what the 3203 online manual says.
Using Rockshaft Control Lever:
Use rockshaft control lever to raise and lower equipment attached to the 3-point hitch.
The six calibrated setting are for reference only and do not signify specific operating depths. When the rockshaft control lever is moved forward, the draft arms will lower closer to the ground.
Lower Implement: Push rockshaft control lever forward.
Raise Implement: Pull rockshaft control lever rearward.
Using Rate of Drop/Lock Valve:
The rate of drop/lock valve controls the rate of rockshaft drop when the rockshaft control lever is operated. This provides direct rate of drop control for 3-point hitch mounted implements. The valve can also be used to hydraulically lock the rockshaft (three-point hitch) in a desired position.
Increase Rate of Drop: Rotate drop/lock valve knob counter-clockwise to make drop faster.
Decrease Rate of Drop: Rotate drop/lock valve knob clockwise to make drop slower.
Lock 3-Point Hitch: Rotate drop/lock valve knob clockwise until tight.
Unlock 3-Point Hitch: Rotate drop/lock valve knob counter-clockwise.
Link to manual
(JD 3203) OMLVU17604_A6