My people!
Really an odd example... and made by a very skilful technician. pehaps in the factory.
According to the sent pictures I can say that not only the complete crate is from pre-war Leica II but also the top plate , rangefinder and viewfinder (windows are slightly greater than FEDs).
Advance and rewind knobs came from FED, but release collar pehaps came from Leica. The speed dial tube of Leicas are threaded and can receive dials from later types and could be machined to receive FED dials... BUT!!!!

in this case the dial is a mistery: It certainly did not came from a IIIf (because the Z) all IIIf have "B" intead. (The 20-1 is Ok but lacks the 1000!) and the speed dial has apparently the same size and engravings of the early FEDs.
So, why not a prototype made for hobby?
According to my point of view, in order to accomodate the new optical system from Leica the top cover was machined and RECHROMED!at the original factory standards.
About the external screw... The position is suspicious! When the camera is cocked in 20 and fired its position comes near the shoe.. This indicates a flash synchonizing device, when it hits a micro switch put as an accessory.
Jacques ! my congratulations for the achievement!
LP