Thanks. Since the traction rating reference is from the Toyo website I shall take the 'c'on their tyre as being just that.
But that toyo site also refers to a c for a temperature rating though it doesnt say where to find these markings :-
The traction rating indicates the tire's ability to stop a vehicle moving straight forward on wet pavement. The ratings are AA, A, B, and C, with AA being the best.
The UTQG Temperature Rating indicates the tire's ability to effectively dissipate heat. The ratings range from A to C, with A being the best.