Not to throw fuel on the fire but the incabloc balance wasn't popular until the '50s although invented in the mid '30s. Could be an ETA 1080 (my first guess at a glance) also still not available until the '50s. Also the fact that it is a center second...........
Add everything up: design, layout, calendar feature, movement - points to a watch from the mid '60s......... in my opinion.
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