We bought our first 401 in 1959 (May or June) so it had to be before 1960. I sold it several years later.
As for Sergers. mine is a pain to thread and I have not talked to anyone so far that does not have trouble with it. So when you find a Serger that threads easily, let us all know because I would be first one to trade mine in.
Gilla
I have a Bernette Funlock 004