Many times bike parts manufacturers stamp a production date into the components. The one I use most often is the date code stamped into the inside of the crank arm. You can also look for a date stamped into the reverse side of the brake arms and in the center of the hub. That will give you a production date within a couple months of the bike being made.
This must be one of the cheaper models as Motobecane used Stronglight cranks on the better models. I owned a Motobecane Le Champion 10 speed for many years before giving it away when I moved on to recumbent bikes. Bikes made in France generally used French threaded components. The Japanese adopted the English thread used by most other brands so French threaded components are hard to come by.