Detroit internal motor part ID needed. Name this part.

Could it be from your air compressor?

 

Its funny truckman would post that pic because the first thing I thought of was a c-clip out of a diff but why would that be in a engine? The head washer is another idea but its got rounded corners if it were a squared off corner I would say its a very good possibility. Its been a few years since I've been deep into a 60 series and this is mind boggling. I guess if its running good with no noises carry on. You could bring it to a detroit dealer and maybe the detroit techs might have a idea.

 

Let us know if you figure it out not going to loose sleep over it but very curious.

 

Is flat on both sides or just one? If one side has a radius it could be a broken injector hold down washer. Could be from last time the injectors were changed. May have fallen down in the head and took its time finding the pan. Wish the pic was better on my phone LOL.