Hi I'm planning to buy a near mint condition M249. The M249 is exactly the same as the M49 except for the connector. I need to know if the Serial# is 5 or 6 digits. When did the production of this mic started? ...And if the first digits of the serial # have any connection with the date of fabrication. Has any of this M249 been produced between 1957-1967? I would really really apreciate your help. Thanks a lot in advance. James D