Ancient History ADS

Is there a consistent method ADS used to identify the year a particular model or specific speaker was produced? I have been in a futile search to undserstand specification and component differences between the respective ADS 200, L200, 200c, 200e and 200i snd same for 300. There is not a specification matrix or any other resource. I am ready to punt the ball after 6 hours of investigatory futility.