A name to attach to the origins of the manuscript

[Jorge_Stolfi]

the parchment could have been produced in-house, as it were, instead of being purchased.

Parchment/vellum making is a very messy and labor-intensive process, even more than paper making.  It requires simple but bulky equipment, months or years of practice, and, from all reports I have seen, it *stinks*.

So I doubt that any ordinary vellum users in the 1400s would make it in-house.  Maybe large monasteries?  I can't imagine the VMS author doing it...

All the best, --stolfi