Nice Watch, I would it is a ref 964. Two views from some 1933 catalogs :
(this last one was issued during 1933 to advertise the creation of 'acier staybrite ', the Omega stainless steel of that period.
Mine is still looking for a decent dial to replace this one made by a blind guy, but nevertheless says hello :
This one is a Naiad CK 2111 with the three slots back. Also existed with a six slot back, I think the three one was the earlier;
A view from the 1940 catalog :
here on the Omega Database :
http://www.omegawatches.com/spirit/history/vintage-omegas/vintage-watches-database?ref=25889 (with a mistake, never existed with a press in back).
Mine says hello :
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