It happens.I don't see why this shouldn't be a genuine NOS Sandoz from the 70'ies. "Swiss Made" only became a legally protected thing in 1971, and even then it allowed for parts of a watch to be manufactured outside of Switzerland. For the movement, e.g. only 50% of the material costs needed to be swiss, but assembly costs didn't matter, for all I know.
I just can't imagine someone faking or frankenizing a 70'ies Sandoz.