Larry,
That's interesting. I understand the main triangle was 531 on the Supercourse, as my sticker said at the top of my seat post tube in 1971. I would be interested in any additional historical information you have, and 'especially' a way to verify if my Supercourse was among "most of the 'Super Course' frames have NO Reynolds tubing at all". This is the very first I have heard of this and wonder how you verified the metallurgy. Likewise, I was wondering if you could retrieve a copy of the "specs" that had a huge variation with no Reynolds 531 tubing.
This is pretty stunning information if verifiable.
Thanks,
Phil Bailey
Sarasota, FL