Ford Rallye Sport (RS) dealer network 1970's..

[CHELT RS]

If registered before 1974 Derby. If after 1974 Nottingham.

https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_the_United_Kingdom

[Redana]

supplying dealer

Thanks for that information its a november 73 car so it must be a RS dealer in Derby at that time then.