From another thread: Several Sturmey-Archer chroniclers have stated the AW hub was "withdrawn and replaced" by the SW during 1955-1959, or for 1954-1960, or for the year 1957, or etc, but, and it's a big but, the AW hub is cataloged in various official Sturmey publications for each of those years. Since the SW hub was more expensive (again, according to factory Sturmey price sheets), it seems reasonable that S-A would keep some quantity of AWs in production for their most price conscious OEMs, and in fact AWs with these date codes do appear on ebay today.