Terminal curiosity

I posted this in Ebay Follies and no way in heck would I buy it for anywhere near that price.. but I'm curious. I assume it's a homemade serial terminal based on the UART and composite.. but it seems like it gets -12v and 5v power from the db25 on the back instead of its own psu? Wondered if that hinted at what it was used with or for.

http://www.ebay.com/itm/121974103853