"Singer did not keep records of actual serial number dates of manufacture for the 301 and 301A as they did with early Singer models. They only used a batch of Serial Numbers, NA-1951, NB-1956, NC-1961. What this means is we must gather our own information to come up with a serial number year of issue. With data I collected over the years from owners of the Singer 301, 301A, 401A, 403A, 500A and 503A I was able to create a year of issue of when our 301 and 301A was issued or manufactured."
got thisinformation from the attached link:
http://singer301.com/dating/default.html