First some summarization:
--A6M Zeros were produced by Mitsubishi and Nakajima
--Around Spring and Summer 1943 topsides received dark green paint as camouflage, factory applied.
--Therefore A6M5, -5a, and -5b models were built and painted at Mitsubishi and Nakajima
--Nakajima used a paint pattern design that featured the demarcation line of the top and bottom paint on the fuselage sides to rise from the wing trailing edge to the leading edge of the horizontal stabilizers.
From here on, I try to figure this out: Was Nakajima also a producer of A6M5c's?