Undersurface camouflages are also a bit mysterious - It appears a large portion (or all?) Rostock blocks 4 and 5 aircraft were rolled out of the factory with the RLM22 undersurfaces; people will cite exceptions/counter-examples to this, but these things didnt not stay pristine for long (ie: a/c suffered crashes on landing or take or, etc; so parts were salvaged and re-used, new parts were fitted, whatever they needed to do - there are at least three plain to see examples of this, if not more!)
D
Those two blocks comprise Werknummern in the ranges 290054-290078 and 290110-290129.
Ferguson argues that aircraft in this range that do not have RLM 22 undersides (citing 290060 and 290059) have been re-painted post factory.
Cheers
Steve