Hi all and thank you in advance. Can you tell me why some books have just the copyright date and other books have the same copyright date plus it reads Library of Congress catalog number with numbers. Any help would be appreciated with this and thank you.
I don't think these things are legal requirements, it's a case of protecting intellectual property. You have to apply for LoC and ISBN numbers, but they become unique identifiers. We see plenty of books here that only give a copyright year. You can't tell from that if it was printed in that year or twenty years later, or if the book is a first edition or 21st, or if it's from the original publisher or not. The more information a copyright page provides, the tighter the control a publisher has on a title, and the easier it is for dealers to know what they are dealing. And then there are the collectors and what they want to know.
Looks like they now call the LCCN the Library of Congress Control Number. I also remember it being called a catalog number. Anyway, according to the LoC, that number is assigned as a precursor to the LoC adding a copy of the book to their collection. And only U. S authors and U.S.-published books are given LCCNs. https://www.loc.gov/publish/pcn/about/#:~:text=A Library of Congress control,record in the national databases. There is also the Cataloging in Publication program, which is intended to help libraries catalog the books for their collections. https://www.loc.gov/publish/cip/