The idea of analyzing the DNA from the vellum that old manuscripts is written on seems very familiar. They will be identifying both the time and area that the skin came from.
There wasn’t much of a blank vellum trade, was there? It seems that the origin of the skin would have been from the same area that it was orinally enscribed. How all of the scraping and recycling of old manuscripts will fit into this is unclear, but it’s definitely a nifty tool.