These pillion footrest rubbers are of the type shown in the 1955 Norton Spare Parts Catalog as being fitted to the swinging arm frame which was used for the Norton ES2, Model 19S and Dominator in the mid/late 1950's.
For this type of frame, the earlier (wider) pressed steel pillion footrest was replaced by a more normal 'bar' type footrest hanger - with this type of pillion footrest rubber. I cannot be sure, but I think this type of rubber was also used on Featherbed Internationals and Dominators. Price is per pair