Genuine Mopar / Chrysler radiator cap part number 5220487 RC12 -9lb. for a number of vehicles from the Rootes group range . The box is somewhat tatty but from a label thereon this cap fits the following vehicles :-
Hillman Avenger all models
Hunter,Sceptre, Rapier and Alpine 1972 onwards
Gazelle,Rapier, 1967-71
Vogue Mk 1-4 1961-67
This also fits the Commer Campervan PA and PB