An odd observation about a recent book club edition

January 19, 2011

Back in the old days, book club editions didn’t list ISBNs, just the book club’s number. Then, a few years back they started listing an ISBN but usually of the equivalent trade edition. For example, the ISBN for the trade hardcover of What the Night Knows is 978-0-553-80772-1. The book club edition (BCE) of What the Night Knows lists the book club number of 1315656 but also the ISBN for the trade edition. (The appearance of the club number and the smaller size, never mind the shoddy binding, indicate that it’s a book club edition.) What this boils down to is that BCE’s don’t get their own ISBNs.
But then today I received my BCE of the large print edition of What the Night Knows. It lists a club number of 1333073 but the ISBN 978-1-61129-143-8. This is not the ISBN of the trade paperback large print edition. (978-0-7393-7797-0) Any searches for this new ISBN online all point to the large print book club edition.
So here’s my question from a bibliographer’s point of view: when did book club editions start getting their own ISBNs? Anyone?