I am not convinced by the provenance history of the VMS

[Aga Tentakulus]

I doubt he could tell apart a 13th centry black parchment from a 15th century one, with any degree of certainty. After all, he wasn't a human radiocarbon machine.

That’s not quite right.
It’s not that difficult to find something with the correct date. Birth, marriage and death registers all contain a date for each individual entry. There are plenty of such registers that still have plenty of space left.
Look up the date, and you’ll have the age.

What’s considerably more difficult is finding the leaflets (such as the Rosette page and the others) from the same period. That’s because they aren’t dated.