As Mike posted above - K1905 was a DH60M Metal Moth (ie metal structure fuselage).
The normal straight winged Moth variants (including DH60M) were deemed unsuitable for Military service due to difficult ingress and egress into/out of the Front Cockpit esp whilst wearing a parachute.
This led to the 'back of a fag packet' redesign of the top wing which moved the fuel tank forward and 'swept back' the upper mainplane for 8 of the DH60T (Dripsy Engine) Trainer aircraft.
This led to the main RAF Production variant of the DH82 with swept back upper mainplane and dihedral on Lower Mainplanes + Dripsy Major Engine.
The dihedral on the lower mainplanes was to increase ground clearance for the wingtips on undulating grass airfields.
Dripsy = Gipsy Engine , Dripsy Major = Gipsy Major Engine
I hope I have got most of that correct - I am sure Mike will put me right if not
