It's a bit of a guessing game trying to work out the origin of Joel Flood's 1950s randonneur.
There are so many features such as the hellenic wrap-over that would point the maker out as possibly Jo Routens of Grenoble, after he had split up from the Hugonnier-Routens business. Routens did and still does use that wrap-over but his version is slightly longer, and more slender, but it might not have been in the 50s. Also he usually used a reinforcemnt col, and lar brazed to the top of the seat-tube whereas Joel's doesn't have one.The seat stay and chain stay ends on Joel's frame are domed and slotted whereas Routens preferred to "chisel" them. Other featues such as the drop-outs, the type of bracket for the Cyclo derailleur, the seat-stay bridge etc are all similar to those used by Routens, but I can't recall him using a metal headbadge...When in partnership with Hugonnier their badge had horizontal hole-spacing. The model is the "Dauphine"..and Routens and Grenoble are in the Dauphine region of Haute Savoie.
However the hellenic style of seat cluster was not unique to Routens...but it may have originated in the Hugonnier-Routens workshops and just been copied by others. Another factor that convinces me that this is not Routens is the fork crown. Routens preferred the two-plate variety..and was still using them in the early 90s..although Hugonnier-Routens were known to use "normal" crowns.
There were quite a few small factories in the St Etienne area..not too far from Grenoble, in the 50s who produced high-end randonneur frames, such as RAVAT, and there was Bourdel in Clermont-Ferrand. Alphonse Thomann in the suburbs also produce some quality frames of this type..and both he and RAVAT used headbadges.
The unusual construction detail on this frame is the use of lugs, that appear to be a Nervex Serie-Legere, or very similar, on the head tube and bronze-welding elsewhere. I have seen this technique on only one other French quality frame..and.. the name escapes me completely..but it was very high end..and from a Parisien builder. I WILL!!! find out.
If Joel could post the centre-to-centre measurements of the head-badge drill holes, that might be a great help.
Norris Lockley..trying to stir "la matiere grise"..Settle UK