Thanks guys,
There's no baffles, the body, 3 pieces, is from 16 gauge, with the tail piece, 2 halves, from 18 gauge with a 3mm wire around.
Really, its an oddity, in the pre war days when the racing guys only needed these things at Brooklands, to assuage the complaints of the residents near the track, most of these cans were knocked together with a crudeness that was almost spectacular
Generally a can would have a couple of 12x6mm bands around the body, and some sort of fin in the triangular space between the fish tail and back of body, in an attempt to cut down the resonance ?
I imagine the one in the photo, with no bands, must resonate pretty badly