Disadvange of this method: I can't encode labels or circular diagrams with
such card, I have to use a differnt encoding scheme here.
When I first read about Steve Ekwall's "folding key", I had pretty much the
kind of mental picture that you painted in your description. Basically, a
spatial filter key.
As you point out, it doesn't work for the circular texts and the labels.
But the even bigger problem is that most of the the text doesn't seem to be
regular enough on the page for it to fit this kind of key. Gaps (between
words, letters, and lines) are irregular, lines are irregular length,
paragraphs fill up to pictures, there are small blocks of text here and
there, etc etc.
Having said that, there are definitely some curious spatial patterns within
the VMS: eg, a few non-horizontal lines of individual characters in various
places. I have no idea what they're indicative of. :-/