Need pics.
1962 or earlier you have a Helyett. 1966 or after you have a Gitane. In between a Griffon and what exactly that meant??
Time to get familiar with ebay.fr and perhaps some of the vendors there. One of the nice things about French bikes is there are huge commonalities between good bikes and cheap bikes. And parts were made to standards that persisted for long periods of time.
If you are happy and impressed by the original paint that is a good sign of an old one. The old striping and decals were wondrous.