We believe that this device is an Atari ST Navarone Sound Digitizer. There are no additional parts or documentation included.
For many years we collected and sold vintage technology items. This piece was mixed in with our video game cartridges. It has a cartridge slot with 20 pin contacts. The side with the audio connections and potentiometers has no cover.
According to our research Navarone Industries is known for their cartridge expanders for TI machines. They also made some games and a disk fixer. I\'ve read about their Clock and Calendar module too.
In researching this device we learned that it was first produced as the Hippo Sound Digitizer before being picked up by Navarone Industries. The December 1988 issue of Compute magazine reviewed this product. The article mentioned that unlike other sounddigitizers of its time, this device allowed the user to playback digitized sounds back using a MIDI keyboard!
Thanks for looking and good luck buyers!