Reynolds 531 ???
 

Is there a fool-proof way of identifying if a frame has been made from Reynolds 531 ?

Sometimes you can see Reynolds and the guages stamped in the tube when it's stripped of paint. Otherwise, unless your mother built it...

The most common place I see the Reynolds stamping is on the Fork Steerer tube just above the fork crown. Good if you know it is original fork and of course presuming a total 531 bike, not just "3 tubes", or "Butted Main Tubes" or other derivations where only the 3 main tubes are 531.

Some bikes marked all 531, notably French makers, do not necessarily have 531 steerers. They often have Nervor instead.

All three 531 frames I've stripped had the faint Reynolds printing on the tubes (one had been decaled as Columbus SL :eek:)

I have stripped two, one Japanese Raleigh 531 and the other a Worksop Competition 531. Only the Japanese one had the stampings.