NOS is an
acronym for New-Old Stock. For those of you that
drive old
classic cars, when it's time to
replace worn items, you look for the coveted NOS on the
advertisement. It means that it was made by the
manufacturer and never sold to a
consumer (the
new part), and the stock was unloaded to parts dealers because they don't make that
part or
car anymore (the
old stockpart).
When I was shopping for parts for my 67 Mustang, 74 GTO and 61 Corvair, it took me almost a year before I found out what NOS meant.