It's going to be tough to get information on items that were made by Music Man in the early years, before they were purchased by Ernie Ball. Perhaps someone here has seen one before.
What information do you need about it? It's a digital reverb unit, possibly custom made or even a one off. Maybe it's a prototype that never went into production.
IIRC, those were private labeled for Music Man by MXR Innovations in 1979-1980, and are pretty rare.
They share the same box/chassis as many of the MXR Rack Mount units from that time period.