Hi all,
I am new here! I was directed here by my good friend Noodia that some of you know!
The picture borrowed from the Net is mine from my watch. The model is indeed called Nautilus Skin Diver. It is the model produced before the double crown super compressor, also using a piquerez super compressor case. The model number is the 6921-1, it was produced from 1958 to 1959 at around 350 pieces which makes it a very rare piece to find especially fully original. The movement is Longines 19 AS. The model was initially delivered with a plastic bezel for the European market and with a metal bezel for the US (watches imported and distributed by Wittnauer). I have seen some with a bakelite bezel which may have been a service bezel since the plastic one on the European version broke easily.
You may find my full review on the Purists forum.
Best
Matt