It reeks of early-Eighties computing. Since there is a dearth of information available, let me recount the mildly amusing story of how I procured it.
Magic smoke plumes.
The computer is toast. Previously, I remembered that I needed a terminal to free myself from console locks common in Linux SVGAlib programming and recalled that a local furniture store had some terminals sitting as displays. I go the the furniture store, get permission, but run into a problem. They want a keyboard. I end up spending some time filing a phone jack to fit in the Plus, only realized that the cords connectiong the handsets fit perfectly.