Late seventies would fit in nicely with what the French were offering - at least in Europe - at the time. Often 3rd or 4th from the top in the line-up, there would be a bike with some sort of proprietary légère tubing, steel cranks and wheels with aluminum rims. Real-world weight would be 25-27 lbs.
I like these bikes. I have a few, and I'm finding that they offered excellent value for money. And still do. New, they were half the price of a high level bike, and these days they are even cheaper, as they're looked down upon by collectors.