All re registered cars now will lose the department number as the new registration plates stay with the car for life (like the UK). Most do have a little department flag to the side normally with the number as the Franchies are quite loyal to their regions.
My traction had the original plate with 31 (Haute Garonne) on it but when I took the plate off it had a painted on number with 64 (Pyrenees Atlantiques) which does match the history – bought new by the auntie of my neighbour who then upgraded to a 15/6 and passed it on to her brother who gave it to his son to learn to drive in 1967, he then parked it up in 1969 in his cousins barn and the next driver was me 🙂
numberplate-history