I don't recall a Super Course, do you mean a Super Corsa? I recall seeing serial numbers as far back as the early 1970s. The lack of one could be due to lack of quality control, which was a big problem particualrly during the pressure of the early 1970s bicycle boom or it could be tied into the fact that high end frames came from other line and may not bear serial numbers.

The French component manufacturers also were not fond of putting date codes on the parts, so that is no help. Your best bet to date it is via frame details, particularly the decal style. If you post pics, I'm sure some member can help you out or you can pick through the catalogs at www.gitaneusa.com . But be aware, that many of catalogs are of French origin and do not necessarily reflect the US product.