Modeldad,
As far as I know, in november 1942, south part of France (so called Zone libre) has been invaded, not only by german Wehrmacht but also by italian forces.
The Groupe de chasse I/1 (G.C I/1) was then equipped with D520s and land-based in the area of "1ère Région aérienne".
The 1st aerial district (extended from Lyon-Bron to Le Luc and St Raphaël, down along the Rhône valley) fell under italian control and near sixty D520 were transferred to Regia Aeronautica, as war-captures.
I believe that the white bands (wings and fuselage) might have been applied on those two D520s by french airmen or mechanicians who did not enjoy to overpaint their beloved insignias too! Overpainting cockades was surely enough for them!
Perhaps is it an explanation for the neat painting job, around insignias?
Hope it will be of some help...