Originally Posted by
Insidious C.
An unidentified 70s vintage French frame has 531 butted main tubes (they are marked as such). The head tube has a visible seam. But the stays have neither an obvious seam nor markings. Are there other clues that would identify the stay tubes?
Precious few. There might - and I stress "might" - be a distinguishing mark inside a chain stay where you can see it from the bottom bracket hanger. Someone may have age-old personal knowledge. There may be some old literature that says. Other than that, I can't imagine how you'd find out.