Parts dry up...
Robert, my guess would be mid 80s at the most recent. But that'd be based on where in the U.S. someone was living at the time….I used to go to scrap yards/auctions/junkyards with my dad in California and by the mid 80s there were noticeably fewer appliances than 10 years previously. These things are obviously still out there, but it's a real scrounge around to locate anything on your own without a network…but like Ralph mentions above --"Prius". It's unbelievable how much metal from the States has become China-bound in the last 20 years.
I'd think where this Amana is concerned, the only way to fix one up today would be to find an identical model (probably in the mid-west) or via another AW member who had to foresight to stash tons of stuff away.