I'm curious how knowing what the items are would help you decide if you want to use them. I was recently looking for a fork crown in my collection, and in most cases, I have no recollection of where they came from. I was just looking for the right width and steerer diameter. There was one that I was really stumped about but I was thinking about using because of the geometry. I figured out it was a Pacenti that I didn't remember he sold. It was high quality, but not exactly a memorable design.

OTOH, for someone selling bikes, it makes a lot of sense to keep track of where something came from and when it was purchased in case there is a problem with it.