After victory in the 1920 Junior TT, AJS's new overhead-valve 350 racer scored a memorable double the following year, Tom Sheard winning the Junior race, and Howard Davies the Senior - the first time such a feat had been achieved on a 350. The production version made its debut in November 1922, delighting clubmen everywhere with its 'racer on the road' performance. A right-first-time design destined to achieve countless successes in the hands of privateers, the overhead-valve 350 AJS - latterly known as the 'Big Port' - changed only in detail before being superseded by a much-revised M6 model for 1929. The latter's engine incorporated a number of improvements including enclosed rocker gear and dry-sump lubrication, while the frame was redesigned to accommodate a saddle tank, and Webb forks replaced the earlier Druids.

This Big Port comes with old-style continuation logbook (issued 1957) listing five owners (Basil Keys from the late 1960s, date stamp indistinct) and old-style Swansea V5.