yeah the disc brake I bought originally in 1995 new to fit my XC51's which I had then. Fits all Marzocchi forks with the thin tapered legs, although you have to drill a hole in XC51 <gulp>!
It's a Hope cable operated brake. The disc fits on a spline to a Hope hub.
The rim as a point of interest is a Campagnolo Stheno - remember them?