My neighbor has a similar JD and what looks to be an upside down hitch pin with a hairpin holding it from the top. It holds a swinging drawbar in place and when you remove it the drawbar can swing.
I have 5520 and my drawbar has this same upside down hitch pin arrangement and the drawbar has a couple of different holes in it so I can remove pin, change holes and have a longer or shorter drawbar length. Takes 10 seconds to adjust drawbar.