[veltro]

IMHO, I would be a little less categoric and attempt a bit of "reverse engineering"...

77x xxx batches weren't produced neither by Erla (we have very experienced researches - Charles Bavaroise and Jörg Meincke among them - who have found original Erla documents documenting production and deliveries of all the G-10s produced by that factory) nor by MTT (the excellent work of Peter Schmoll documents the whole Bf 109 production of that factory), so what is left? WNF of course.

Further, the fact that camouflage does not resemble that of Diana examples means only that they weren't produced there, but Diana was only a separate production center, this does not exclude at all the G-10/R2 production at Wiener Neustadt.

Last but not least, there are many photographs available of abandoned/wrecked G-10s without the plate/battery cover on the rear cockpit angled "wall", resulting in a trapezoidal hole not necessarily linked to a K-4.

Hope it helps.