By the mid 80's, the Tange 2 was about 2.2 oz heavier than a Tange 1 for a 58cm frameset, per what I've read, but actually riding a 56cm Tange 2 Lemans RS vs a 56cm Tange 1 Ironman, I can't tell, weight-wise. The geometry is different enough, however, to be noticeable.

I'm pretty sure if I was blindbolded and put on a bike, the geometry would be something I could tell from bike to bike, but the weight, not.