Door seals and "C" channels

[alunwill]

Does anyone know if all series 1 cars used the "C" channel rails to keep the door seals in place. Mine's a september 66 car which had them from new but I've seen August and November 66 cars which supposedly didn't have them installed from new. I can see it being individual choice today but was it this way from the factory or just ommitted over time because the later cars had better seals.

Al