It's a DEC LK421, designed for use with DEC's Unix terminals and workstations of the early 90s, and almost certainly one of the main inspirations for the HHKB. Not immediately PC compatible, but the protocol used by DEC's keyboards is well documented, so it should be easy to make a conversion.
Also, the particular one I'm getting was an Engineering Prototype, which makes it even more awesome -
The mouse is also quite interesting. They were made by a company called Hawley, and instead of a ball, they used two angled wheels, one for X axis, the other for Y... They were supposedly a good bit better than contemporary ball mice, but they never caught on, being too expensive for the regular market, and probably not as good as early optical mice for the high end one.
All this for about 50 euros including shipping to Europe