I will try and answer your question regarding the difference in measuring
lands, then maybe others will join in the fun.

It was always explained that
1)  on the external lands the plating was in contact with the entire surface
of the land - so if there was disattachement of the plating from the very end
of the foil, there would still be an intact connection from the land to the
end of the plating in the hole.

2)  with inner layers - if the plating becomes disattached the inner layer
only
consists of the inner layer itself

Susan Mansilla
Technical Director
Robisan Lab

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