Two Seven Twenty Audio Transducers. These work on a different principle than normal speaker. They bolt to a solid flat surface and then vibrate that flat surface to generate sound. Or something like that. Theoretically, sound that hit the flat surface would be converted to electric current that could be recorded or transmitted. I think. These were making sound from an am/fm radio on the boat we bought. Probably from the early 1970s. The company that made them seems to be defunct. These Condition is "Used".