>>>Once upon a time, I had a mid-80's Trek 660....and you are right, it was heavy. I think it was all the investment casting: seat lug, bb shell, fork crown, brake bridge...even the dropouts as I recall. I had friends who refered to it as the 'cast-iron" bike. Skip Sinatra<<<<
Just for reference, my 1984 Trek 660 frame, 531cs, with a Record BB and Stronglight (A-9?) headset installed, weighs 7 lbs even.
Wayne Bingham
Lovettsville VA