Historic Motor Racing Groups or Classes Ja & Jb Vintage Cars (Pre-1931) Ka and Kb Post-Vintage Thoroughbred Cars (1931-1940) Lb Sports-racing & racing cars 1/1/41 up to 31/12/60 M Racing & Sports racing 1/1/61 up to 31/12/65 Nb Production Touring Cars (Pre-1965) Nc Production Touring Cars (1965-1972) O Racing & Sports Racing Cars (1966-1969) Formula 5000 Racing Cars (Pre-1978)(Group P) Q Racing & Sports Racing Cars (1970-1977) Sa Production Sports Cars (1941-1960) Sb Production Sports Cars (1961-1969) Sc Production Sports Cars (1970-1977) Regularity Ja & Jb Vintage Cars Ka and Kb Post-Vintage Lb sports & racing cars M racing & sports racing Nb Production Touring Cars Nc Production Touring Cars O Racing & Sports Racing Cars Formula 5000 Q Racing & Sports Sa Production Sports Cars Sb Production Sports Cars Regularity