The paint on that bike does not look like the same shade of blue that Gitane used in the 80's. From what I see on the pics, the paintjob actually look very fresh and could already be a re-paint and it looks like they did a good job at it. Just a bit of polishing should bring out some depth and luster to that paint. The mysterious paint color just deepens the mystery on what the frame really is. I agree with BG that the letter in the BB shell looks more like a "W". It cergtainly a mid 60's to early 90's frame with the very vertical rear dropout configuration.
That's a very beautiful frame and you made a good decision to go ahead and get it! Congratulations on the fantastic find!

Chombi