Marc, this would be an extremally difficult to proof.
You see, the oil tank is bigger, the cooler is shallow and no chin bulges. The panel under the windscreen is square and the crosses on fuselage are smaller.
The mainwheel are bigger and the tailwheel is lower.
The camouflage is characteristic too to those to be surely G-10 from 151/152 bathes.
The G-14/AS built by Erla I know of were just preety different in both shape and presence.
With the maintance - I do have a look for a large collection of photos from Neubiberg. Those Gustavs are so different in apperance, some are filthy, some are almost clean.
The same with more photos of abandoned / damaged ones from german abandoned airfields.
I'll go with a G-10/R6 rather well maintained or well cleaned after all.
