As far as I know, the Reg Harris branded Lamberts were rare, although it's only a sticker! The frame would have been made around summer 1972, outsourced as the first job of a new company set up by two builders known to Bob Thom when a local bike company moved out of Wolverhampton, and probably a variant of one of the better Viking frames and well-made. The tubing was lighter and stronger than 531 and a lot cheaper. PM me if you're interested.