Originally Posted by
verktyg
Reynolds 531c (Competition) was a lighter tubing set. It wasn't introduced under that name until 1982. Prior to that it was called 531SL or 531 Special Light Weight.
I disagree with this. It reads like 531c and 531sl are different eras of the same tubing. They are not. 531sl is substantially lighter. It is really easy to feel this difference under you if you ever get the chance to ride a 531sl bike.
The way I understand it, 531c is simply an easier way to say full 531 tubes, forks and stays. So, my '60 Paramount is basically a 531c bike even though it doesn't say that on the decal like my '87 Falcon.
edit: I also still disagree with you about the Grand Record as I already mentioned. My opinion/experience on this is also reflected in the Moto catalogues.