Jindabyne,
That's the first Whirlwind 10 I've ever seen outside the Far East with the sand filter door. If that was '65, it would have been one of the first, I think, to have got the door.
It was probably a good idea in Aden as GW 1 showed further north but in Borneo it was regarded as 84 lbs of worthless weight, which reduced the payload/fuel and for little tangible benefit.
Old Duffer