That's exactly it, Straffo. The pilot boarded the '38 by means of a ladder which lowered from the rear left wing near the fuselage. He climbed up this ladder and walked on the wing to the entry point.
Also, if you note the fuel cap positions, I imagine it would've been common for refuelers to be climbing all over this area, dragging their fuel hoses around, wearing and chipping away the paint.
Really a nice touch on Kev's part.