I can't make out a gray wire on the ground block, but if it's there, it makes for an interesting conflict with the gray used as a phase on the main GFI at the bottom!
I hadn't notice the different fuse on phase C of the top left unit either, but maybe these are three individual single-phase circuits? Looks like only a single neutral going into that block though.
It also looks as though it's an open back unit with just the mounting rails screwed directly to a plastered wall (David - It brings to mind the open-back Wylex consumer units which are still to be found in great quantities here.).
Another point: Those main incoming conductors bottom right look as though they're just single-insulated cables buried directly in the wall. Or is there perhaps a conduit that we can't see?
