Marzocchi Fork Slider

[chbevelbob]

Hi
I'm renewing the seals on some 38mm Marzocchis and noticed the following:-
On one slider the seems to be a "hole" on the inside of the casting i.e. where the stanchions go , opposite the brake mountings,
about the level of the mudguard mounts . Not very deep and only on one slider.
Is this standard, ? Any ideas what this could be for ?
Thanks for any info
Best regards
Bob