If you go to the vintage Trek web site, you may be able to figure out frame materials and original components by using the bike's color scheme to ID its model year.
I know that for at least some of the late '80s/early '90s, the 800-series frames were made in Taiwan, while the 900-series frames were made in the USA.

My best-ever craigslist purchase (a few years ago) was a '96 Trek 950 for $47; it had a few nicks and scratches and a bit of surface rust on the gears, but a few hours of rehab work along with new V brakes and chain and upgraded (but re-used) derailleurs and it's now a rock-solid "backup" bike.