By accident I got a XC250 by exchanging parts and seals for a XC51.
This fork is something like a rumour, because if you try to find something out about it you will find very, very less informations about. Even Google shows only a few pics, which are very unharp, and a small amount of links, mostly useless.
The fork looks like a silver XC500 regarding sticker, brake booster and tube design (with holes), it’s casting shows ’93 (1993).
The Marzochi XC250 is e.g. published here: