I'm never going to find a b-day Model M.
Maybe a super early Unicomp if I'm lucky. My Unicomp is from 2001, but that's a year off. Close enough I suppose
Completely opposite of what this thread intended to ask, but were there any SSKs manufactured in the year 2000? And to answer the original question, the oldest SSK I have seen was from 1988 IIRC.