Originally Posted by
Dark Side of The Loon
The main change is the correction of the error Zenith made by going from the original dial layout, to one in which part of the running minute sub-counter was obscured. The original dial layout has the overlap occur on a small part of the running hour counter, which could be read just as well with the overlap as without.
I seem to remember reading something about this change being made on the insistence of Jean-Claude Biver, after being pestered by collectors/enthusiasts about it. I don't have a source for that, though, so it could be nonsense.
It's difficult to fathom how the mistake was made in the first place, but it's good that it has been fixed.