Jerome is talking about prestigious pedigrees. It's nice to know that your coins come from famous
collections, e.g. Hall, Ryan,
Jameson, Trau; or were acquired by exchange from a museum, say BM; or were in a high-quality sale such as Ars Classica, Leu,
Triton. I don't think such a
pedigree has much effect on the
price of a coin, however, except in the case of the Gonzaga eaglet.
For a scholar who wants to include your coin in a study, however, EVERY known detail about its
provenance is important, in order to eliminate possible double counting of the same specimen, and especially if the
provenance indicates a probable findspot. For example it's important to record that your coin came from a
Bulgarian supplier, however humble, because that means it was probably found in
Bulgaria!