Hi Bill,
According to Wikipedia the French were using the FNI system from 1950 to 2009 – which means the car would be registered in the department it lived in.
https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_France#FNI
The format would be 123 AB 12 – where the last 2 letters were the department code.
79 refers to the Deux-Sevres department which is on the western side of France about half way down
https://en.wikipedia.org/wiki/Departments_of_France#Current_departments
Chris
Chris