Seems familiar to me in my scrounging junkyards a while back.
I saw something very much like that on an old stationary DD engine on a pump
system. The odd thing was that I don't remember anything but a blank cover on
what we refer to as a governor housing with a setscrew and locknut.
I think it may have been an old DD 671 or pretty close.
What you describe is a method to pull the rack closed and shutdown a fixed
I wonder if somewhere along the way that parts from an old stationary engine
were added to yours or maybe you have a transplant??
Sorry, The old brain just ain't up to remembering exactly about this stuff.
Been a long time ago but it was a truck and industrial salvage yard.