I know of a model year 72 S RHD Sepia Sportomatic kept in very nice condition by friend who is car's long term owner since 80s. Assume not many examples were sold this side of the pond that year with that particular configuration.
By the October of 72 for model year 73 a 911 S with Sportomatic was about £25 more expensive than the Carrera RS Sport (M471) as listed on the same UK price list so not sure how many they sold that next model year, year brown or otherwise. Likely rarer and less hard use by rally and racing community if any were bought, however.