Good question. Don't really have an answer but since it's attached to the throttle control lever one would assume it has something to do with that. I looked at several detailed Bosch drawings of VE pumps and didn't see it. Do you have the Bosch model or Cummins part number? Might be a part that was specific to its original application.
Here's the tag that came with it spent last night putting my 3200 governor spring in turning up fuel adjusted low idle down disabling KSB & removed fuel shutoff plunger. I just have to turn fuel pin then install and hope for the best🤣
That tab goes under the bolt that locks the shaft. Right now your pump is locked by the bolt at TDC (probably). When you install the pump, you back the bolt out a bit and put that spacer under it in order to snug it back down without locking the shaft.
Im not sure but I knew from stuff I read and watched about that timing lock I just wanted to be sure as it was wired on the pump so I knew it was for something important 🤣 1100$ I definitely knew I'd better ask🤣