Late sixties, possibly as early as 1967 (first year for white paint, except for team bikes, which were white earlier).
This bike will require a French threaded bottom bracket. Frankly, either get the original stronglight or get a phil wood bb. Bike is too nice for any of the other BB treatments I'd give a French frame.
Looks in very nice shape. Seems a bit pricey, but the big city market is like that (where is this bike at? SF?).
To give you some idea of pricing, I paid 455$, including shipping, for a complete PX in excellent condition from the same period (same size, as well). I'd try to talk the price down a bit.
Bike will require a Simplex rear derailleur as the dropout is simplex; unless it has been tapped out to take Campy/Shimano stuff.