Like was stated earlier, you kinda have to read between the lines on the serial number prefixes. Those prefixes are what was turned into them before publication and confirmed by S&W. So if you have something that falls close to it but is not listed you have to guess it would be close to it. Thats why BNY is probably from mid '93.
Also, the 649 nor any other Bodyguard model was ever authorized by NYPD for use. As far as J frames go it was the 36, 60 (for a very short time and then no longer allowed), and the 640.