The most common dealer fit radio was manufactured by Motorola... Usually a 4TMB or an 8TMB. These are the ones with "Sunbeam" on the dial. These radios could be switched for Positive or Negative ground and were also sold to/for BMC (Healey/MG/Jaguar) and also Triumph. All with the marque name on the dial... The BMC ones were either marked BMCD or British Motor Corporation. Sunbeam radios read "SUNBEAM" and until 1968 the ones for Triumph, were labels as such. After 1968 and the Leyland Merger, they were marked as "BL" (British Leyland) as were the former BMC marques. These were a single speaker, push button AM band radio... Rootes cars were positive ground until they started fitting alternators... so a series 4 Alpine was Pos. ground, while a MK1 Tiger was negative ground. The same radio was optional in the USA for either... It was just a matter of setting up the radio for polarity.