Thus it isn't likely to be aviation related.
Looks to me like some kind of Naval synchro/repeater as suggested above.
The restricted arc is big clue and probably rules out a wind instrument. That arc is to do with aligning something that needs to be accurately positioned within 30 deg of "ahead" and less accurately on the rest of the arcs. The restricted arc implies that for some reason it cannot be placed between Red 60 and 180. Figure what that might be and we'll have an answer.
Likely to be something not mounted on the centreline but that has limited movement across it to the left like Stbd side armament on a cruiser or battleship.
A deck crane perhaps? Torpedo tube? Not something requiring much precision like a range finder for instance.
AA/high elevation gun might fit though the emphasis on the straight ahead markings doesn't seem logical there.