Echo mic from my uncles CB collection. He operated a large base station and this was with it. I finally got around to testing it, it does have output seen on a scope, you have to lean into the foam quite a bit. I was also using a borrowed 9 volt from another device, so I’m not sure if it would have better results with a fresh battery. That was the only testing I did, didn’t have anything to hear the audio quality with.

Sold as is, as shown.