I have an old AV S-2020 microphone and I am curious as to when these were manufactured? I know that it is probably not worth much but I would like to know more history about this microphone.
Your mic is in the same series as the 515 series. The 515 series is still made and has been around since the late 1960s. One version of the S-2020 was sold to Perma-Power and was packaged with the Perma-Power lecterns that had self-contained amplification systems.