Its from a 180d engine around 1956. The diaphragm is the shut off, and how it senses throttle. No direct connection, other than vacuum to the pedal. It doesn't have a splined socket, just a normal hex. Those flat barrels did come out, I didn't see any type of pin to hold them in a certain place.

This is super antique diesel stuff. I freed everything up, and clean. Then I started to snug up everything by hand, and the rack jammed. When it jams, the valve springs inside don't reach the large barrels that ride the wee crankshaft.