83 years young, we don't see enough 40's watches here.
The Art Deco dial face looks the same as the Smiths synchro electric mantle clock we had when I was a kid in the 60's
Iridescent azul excellence! - ca. 1971 Mathey-Tissot “Mergulhador” Skin Diver - Ref. 1635 - powered by a “Ultra High Frequency” (UHF) ETA 2784 automatic movement. (f ~ 28,800 A/h vs. 21,600 A/h) - Mergulhador meaning “scuba diver” in Portuguese, which makes since as many of these carry a Portuguese import stamp.