The above statement, by Henry Bradshaw, could be the official Creed of the provenance researcher.
When discussing cataloguing, I sometimes tell people that I think that the single most important thing a cataloguer can tell their reader about a manuscript is its collation. (This is partly, but not exclusively, because the physical structure of leaves and bifolia is one of the few features of a manuscript that usually cannot be conveyed by photography). People who study manuscripts -- and early printed books -- seem to fall into two camps: on one hand there are those who see collation as a mechanical task, like measuring the leaves and counting the number of lines, and on the other hand are those who really understand how much a book's physical structure can tell them about its manufacture, and know how to use this powerful tool to inform their work. I won't go into details here; I mention it only as background to explain why Henry Bradshaw is one of my bibliographical heroes -- on a par with M.R. James and Neil Ker.