The serial numbering system did not change when AMF bought the company. It is still a CWC bike. AMF also bought Harley Davidson in 1971 but we don't call these AMFs (although some hard core HD folks call them something else!). As far as I know Gambles was the exclusive distributor for Hiawatha branded bicycles whether they were made by Shelby, CWC, or anyone else. I understand your frustration concerning bicycle research. I am also a car guy and with an automobile serial number I can discern a wealth of information. With bicycles a serial number may tell you nothing. This coupled with the fact that the literature is fragmented and incomplete leads to a lot of gaps. I believe a lot of info was lost when these companies were absorbed and the records were destroyed. Even the contemporary catalogues that exist are not comprehensive or totally accurate in many cases which further exacerbates this problem. Welcome to our world! Best of luck with your project. V/r Shawn