Assumptions baked into the VMS carbon dating

[Koen G]

If we accept Taccola as a source, this would place the lowest boundary for at least the Balneo and Cosmo sections to the 1420s. More realistically the 1430s. The older 1308-1362 peak implies that the parchment [of that section] would have been at least 60 years old when used, even up to 125 years.

  

No objections to that for the Balneo section.  But is there any plausible Taccola influence on Astro/Cosmo, which contains f68? 

Not necessarily for the Cosmo diagrams, I think.  But the fact that some of the celestial bodies are personifications (full heads) rather than just having a smiley face is either very early (inherited from Classical sources) OR broadly renaissance (Taccola does this as well). If we move into the Zodiac section, the fashion of the figures is not plausible before some time in the 1390's.