I found an interface I've never seen, a Fisher Rosemont Highway
interface. I don't know much in the history of Dec / VMS, but am
guessing this is for Vax system only.
I found this flyer sheet about it with the info on the interface. I'm
guessing if you don't have one of the central boxes, you have some
expensive gold scrap in these boards.
The fact this reference is where it is suggests there must be embedded
systems using it to justify the price though. Also the other manual
referred to indicates that there is something that runs on NT, as well
as a mention of AIX.