This is a very odd watch. The balance cock is all wrong for an 861. Not only is the eccentric screw missing, and the regulating pointer is not hollow for that screw, but the stud carrier appears to be the wrong colour. If you look at the balance spring coming out of regulating pins, it makes a very odd nearly 90 degree turn, like someone tried to fit the wrong balance to the watch. Edited to add this photo - this is not what the spring should look like.
Okay it might just be the angle of the photo making the dog leg look very extreme....would need to see another photo to be sure...
The colour of the balance wheel is also wrong. I'll be surprised if this runs well, if it runs at all.
The bezel insert looks like it has been removed, and really doesn't fit the bezel well - might have been machined down to fit, and done very unevenly. Even the crystal looks off to me - like it is a much higher dome that a proper Speedmaster crystal.
As far as the lack of watchmaker service marks inside, well if I was involved with this watch, I certainly would not want it traced back to me, so maybe not too surprising there are no marks.
I know you want to believe this is something special, but I think if you take the emotion out of this, it's just some put together watch mate...and a very bad one at that...
Cheers, Al