I concur with Caterham's comments. Furthermore, the top end of the range can reduced to 1982 based on the tubing decal, unless Bertin had old stock decals left over.

Japanese components would not be out of place for a 1978 french bicycle. The boom had collapsed in 1975 and you could no longer sell just any 10 speed. The market had become fiercely competitive for the reduced customer base. Consequently, value for the dollar became extremely important, particularly at the entry and mid-range levels. This was an area were the Japanese components excelled. Shimano 600EX had a big advantage here. Shimano 600 had been the first complete mid-range group and 600EX upped the ante with improved performance and features, and more ornate, unified aesthetics that approached the look of Campagnolo's top groups, at a fraction of the cost. Bertin had placed himself well for the changing market, becoming the European Shimano distributor in 1975. Other circa 1978 French models with Shimano 600EX inlcuded the Gitane 600 Kreger and Motobecane Sprintour. The only major French manufactuer who still used 100% French components was Peugeot.

Personlly, I think it would be a shame to part out such a lovely example. Why not put it on Ebay or C/L with a fixed price that would recoup your investment? You might be suprised as the offers you get.