A four-inch speaker mounted in a wooden box with an audio amplifier that has bass, treble, and parametric mid-range controls. Not sure what the "noise limiter" does. Sold by Grove Enterprises and reviewed by Bob Grove himself. I would expect nothing less than glowing reviews.
Bob Heil is now selling roughly the same thing for $269 without the speaker. Bob gives it good reviews, too.
Parametric Receive Audio System Equalizer (PRASEQ) | Heil Ham Radio | Amateur Radio
Most radio communication audio systems are designed to pass 300 Hz to 3000 Hz. The first step to developing an equalizer, amplifier, and speaker for communication monitoring is to limit the range to those frequencies. Then, add a parametric mid-range control to the equalizer so you can "sweep" the center frequency of the mid-range boost/cut in order to somewhat isolate a specific range of frequencies. For listening to CW, instead of voice, you'd want a much narrower audio range.
Yes,
@Gumball928, you got a good find. It would be useful for monitoring any radio traffic. Just hope you didn't pay too much for it.