Looks like a conversion to run on an open center tractor.

More info about all of that

http://talk.newagtalk.com/forums/thread-view.asp?tid=612538&posts=1#M5115295

This came from someone on Ag Talk originally so hope they will chime in and talk more about this.

https://www.youtube.com/watch?v=vjkDxacS5Ss

Found the thread where it was discussed by K-Tech

http://talk.newagtalk.com/forums/thread-view.asp?tid=546445

K- tech made the original post and the Youtube video so hopefully he can chime in with any more additional info.

http://talk.newagtalk.com/view-profile.asp?action=view&uid=15895