Thanks, I had never seen this transfer sheet before. So the info I thought I read about 531c was really about 531cs. A few more questions for the experts. My '84 Trek 760, according to Trek brochures, was supposed to be in 531p - is that the 531 Professional? My frame's serial # dates to 1983, but with the changed '84 lugs and paint scheme, but seemingly with the '83 531c tubing - or did builders not use 531p above a particular frame size (ala Columbus with SL/P and the X series tubing) - mine's a 58cm? And one more, in the same article I referenced it had Reynolds 501 as a seamed tubing - is that correct? Thanks again.