List, Thanks for the replies, on and off list, to my inquiry about 531c vs. 531 Professionnel tubing. No doubt this subject has been discussed before, but I'll summarize, in case anyone else is interested.
One list member very kindly sent me a fabulous full color scan showing 40 different Reynolds decals with brief descriptions. Actually, there are 20 different decals, but with English and French versions of each, the number is doubled. Ironically, this info sheet from TI Reynolds has a typo on the very decal of interest to me, the 531 Professionnel. They show the French version of the respray decal rather than the decal for original work.
The 531 Professional decal stands out because it is red, black and gold, rather than the familiar green, black and gold. When you parse the descriptions of the 531 Professional vs. the 531 Competition, the two really sound quite similar until you notice the phrase "very light gauge Reynolds 531 tube", applied to the 531P (my abbreviation, not used by TI Reynolds). Evidently the same alloy, but rolled it thinner. This possibly means a sacrifice of long-term durability or general ruggedness in favor of reduced weight. The 531C is claimed to be good for road racing, track, time trials, and cyclo-cross, whereas the 531P is designated for road racing and time trials only. Also, 531P is designated as the successor to 531 SL, having "improved weight and performance characteristics". Sounds like there might be an element of damage control by the marketing people here.
Have a good weekend, everyone.
John Hurley
Austin, Texas, USA