some of later taiwanese ones still said chicago...but that and old catalogs and serial numbers will tell you a lot. it's all online, too. but a few things...

electroforging = bad.
oval headbage on a schwinn = bad
doesn't say "chicago" = probably bad
weighs a ton = bad
ashtabula cranks = bad

for starters. it's a shame, i guess, that it's hard to just find a really great old schwinn lying around, as most people with nice schwinns seem to know so. ah, finding one of those old chrome schwinn paramount track bikes at a garage sale for 15 bucks would be glorious....but i don't think it'll happen.