atalamark-

I think it may be a C 70. This was an entry level racing Bertin with light gauge hi-tensile tubing. It was well equipped with quality components at the cost of a slightly heavier frame / fork. The typical clue to this is the AB diamond decal. It is often found on the down tube of most Bertins but C 70s almost invariably had them at the top of the seat tube. The 25.8 mm seatpost also indicates plain gauge hi-tensile. Higher spec French tubing usually was in the 26.2, 26.6 or 26.8 mm range for seatpost sizing. Charles should be able to add insights here as the detailed shots have arrived. It's a nice looking frame and I hope you enjoy it.