CMP Fender to body joins

[Bruce Parker (RIP)]

I'm forming an opinion (though welcome to be rebutted) that early CMPs used a civilian rubber seal, flat with a round outer that was soon replaced with a similar product made of canvas impregnated with 'tar'. What is certain is that a flat example of the tar impregnated burlap/canvas was used as a roof gasket at least on CMP HUPs. Distant memory perhaps, but on my 1944 HUW I wonder if the fender bead was replace with the flat seal. I think I would have noticed a bead and recorded it when taking them off.