Hello again everyone!
I'm reviving this discussion because I just came across a photo of Bernard Guyot taken in 1968 on his Sauvage-Lejeune-liveried bicycle, where you can see his initials engraved on the seatstay caps, the signature of a frame built by Bernard Carré for professionals of the time, such as Jan Janssen from the same team.
Jan Janssen, 1965