Many thanks for posting this. Another fascinating Helvetia
It always amazes me seeing the ingenuity companies (and individuals) went through to solve the practical issues of the day, and it gives a great insight into the evolution of what we are all too ready to accept as "standard" today.
Some lovely engineering too, and nice to see the Geneva stripe adaptation on the rear of the movement.
Is there any kind of gasket at all, or does it rely solely on the pressure between the metal of the bezel and the case for the degree of water proofing?