How quickly did the VMS leave the possession of those who understood it?

[Jorge_Stolfi]

The most conservative estimate is that at least two people worked on the text, which is considered original to the MS. So at least two people knew a lot about the MS.

Whoa, not so fast.  

There may have been two or more scribes who put the thing to vellum.  But, again, it would be insane for someone to write straight from one's head onto vellum.  For several reasons. 

Therefore, those scribes almost surely copied from a draft on paper, that had the text and sketches of the figures in some uncertain degree of detail.  

But then there is no reason to think that there was more than one person who understood the text and created that draft.  All that the scribe(s) needed to know in order to copy the draft to vellum was the alphabet.  They did not even need to know what it sounded like.  

Maybe one of the scribes was the author of the draft himself.  But the apparently misaligned half-lines of You are not allowed to view links. Register or Login to view. is evidence (not conclusive, but not negligible) that the scribe who wrote the text on that page could not read it.  

Moreover, not everyone would be able to draw on vellum those tiny letters with a minimum of neatness.  Thus it is more likely that the Author (or Authors, if you will) enlisted other people to do the actual scribing on the vellum: if not experienced "professional" scribes, at least someone who was able to do that.

All the best, --stolfi