The XC400 is something like an old style hero, look at the holes in in the bottom legs! The style continued in XC500, XC600, XC700, DH3.
Most of it – I think ALL the 24mm forks – are using the same seals … I believe from Star Fork until XC500. The XC400 has an air/oil separator and a more specific damping environment (look at the black screws left from the bottom tubes in the middle). It also has the air caps + o-rings, plastic caps and the circlips, which are used in XC500 and others.
to be continued …