Originally Posted by
boneshaker78
Stripped the frame and found stamp on down tube. Reynolds 531 Butted 20/23! That may help figure out the manufacturer.
No, that is not particularly useful information to lead us to the manufacturer. Reynolds used to mark their tubes to identify it was 531 tubing (they had other models) and the wall thickness. 20/23 describes the sheet gauge thickness that is roughly the equivalent of .9mm/.6mm. This was the most common tubing used by American builders in the late 70's. Actually all the parts of the frame look like pieces we could buy from American suppliers back then.
I've repainted hundreds of frames since the 70's and think this is most likely American made. What makes me unsure is the binder bolt. It looks like a binder was brazed onto a lug without binder ears. Japanese Nikko lugs didn't have ears like Prugnat lugs but these look like Prugnat lugs. They don't look like Nikko lugs at all.