These petrol tank kneepads, with the Norton logo embossed in them are of the type fitted to Norton International's through the 1930's and into the early 1950's. This was also the type fitted to most SV and OHV model petrol tanks through the 1930's and until approximately 1953, when a slightly more bulbous tank was introduced on the ES2, which I also sell - Item Number 0419.. I am also able to supply the chromed screws that secure them to the petrol tank.
Note: these are sourced from a UK company, not the Indian version often seen on Ebay, I have compared both side by side and found these to be a much better reproduction - hence price slightly higher than some seen on Ebay