Palatino 766 pipes, pools, cliffs, streams... (by Taccola)

[Jorge_Stolfi]

For me, Siena is a bit outside the likely area of influence for the Voynich MS, both geographically (it is quite far south) and timewise, though that is definitely marginal. There would have hardly been any time for the MS to 'spread'.

Any match between VMS images and images of Book X only implies that the Scribe had access to a copy of Book X, or a copy of whatever source the images of Book X were copied from.

Therefore, the geography does not seem to be a problem, since Taccola's work was well-known north of the Alps. 

As for the time, it is quite possible that the VMS was written several decades after the vellum was manufactured.  It may have been sitting in the "rejects" trunk of the vellum maker for that long, until the Author came asking for the cheapest vellum they had...

All the best, --stolfi