Silent Saloon.

[Duncan Grimmond]

Regarding the half-round spare petrol tank, the capacity cannot be more than half a gallon.  I have the Desmo catalogue for 1934 which shows their one gallon wing tank for the Austin 7, which is square sided with a slightly domed top, and much larger.  It cost 8/6 in 1934.
Presumably the small half- round tank slides out of the fixing brackets once the retaining collar over the filler has been hinged up out of the way?

I can't see how the neck fixing (which seems to be hinged) could move enough unless there is a wing nut under the wing (not a good place). Slacken the nut and lift the rear edge clear of the mounting allowing its withdrawal from the ring?