I don't know if this has been posted in this thread, but this is from Phil Marshall the Cleveland Welding guy ,
(my serial number is D73867)
I think I've posted this earlier but Phil is very knowledgeable on CWC dating.....
The key to dating your bike is the Cw symbol stamped after the end of the serial number. CWC ran through the same serial numbers several times from 1935 through 1956 and for postwar bikes the key to dating them is to first recognize the features that define them as postwar frames and then look for the symbol that follows the serial number. Bikes with the Cw stamp were from the second postwar run through the alphabet and the first bikes in this series rarely have the Cw stamp. By the time “D” was reached the suffix stamp became quite commonplace, probably to begin separating the series from the first wartime or postwar “D” serialed bikes. My best data-modeled estimate is that the Cw series was produced from 1947 through 1949. The exact transition from the first series to the second series is still debatable so I have slid the scale a bit several times to try to align it with actual bikes, ads, and other factors to come up with the most likely scenario. The second postwar serial number series bikes were produced with serial numbers ranging from A00001 through J99999, assumedly in sequence. A bike with a “D” serial number would, following this logic, have a build date in approximately mid 1948.