Let's see if I can help you out a little bit.
According to SCSW #3;
-Serial number 7554xx puts that gun in the 1962-1969 range. ( I cant clarify further with this book because the serials range from 295000-786544)
-Serial number R2332xx puts that gun in the1979-1980 range. (serials numbers for this range are R220001-R280000)
Hope that helps a bit
