If you haven't already seen this (below), it is a good explanation of the various Japanese-manufactured tubes used on some 70's - 80's vintage bikes - on the Retrogrouch website. The posting and some of the comments are helpful. It helped me better understand the quality of some bikes/frames that I see on Craigslist.

Retrogrouch makes the case that some of the Tange and Ishawata tubes are of a comparable quality to the better Columbus and Reynolds offerings - and this means that some vintage bikes are under-appreciated for the quality of their frames thereby relected in asking prices. ....may be some bargains out there...


The Retrogrouch: Classic Tubes: Tange and Ishiwata