The frame is a 1969-1971 Gitane Tour de France that someone has done some nice file work on.... namely the seat stay caps.
TA cranks, derailleurs, seatpost, seat. bars and stem are replacements.
Someone did a nice job on the frames.
26.4mm was the standard seatpost size for those frames. Someone could have reamed the seat tube/lug out to 26.6mm but .2mm is a lot of material to remove. There's a slim possibility that the frame was made with lighter gage Reynolds 531 tubing but 28mm seat tubes with a 0.7mm wall thickness at the top was standard on most French production frames back then (that's why 26.4mm is the standard for seatposts on those bikes).
verktyg
Chas.