The original 1,000cc engine design with cast iron cylinder barrels and head remained in production until it was superseded in 1949 by an all-alloy model, later designated the 4G Mk I-1000cc, when a newly-developed, four-exhaust-pipe cylinder head was introduced in 1953. The new, all-alloy model became known as the 4G Mk II-1000cc, or 4GII, and remained in production until 1959.
This example is one of 3,828 produced of that last Square Four model.
