Postcard with Norton 16H under rider maintenance?,one has what looks like folding oil can in his hand?,large oil or grease can near by and tool kit on floor,says Royal Signals on back?.

Thanks Steve. The cap badges certainly look like R. Sigs and I always like toolroll photos :-)

C415**** was from the 1940 contract C5612 - just about the last to have retained the central speedo mount.

Are you able to read the full serial number at all ?