Time for one of the dirty little secrets of cataloging. Call numbers are not permanent, never have been, never will be. This is not something that’s widely known, even amongst many librarians it seems.
Right now I’m working on a large recataloging project and I’m hamstrung by some finding aids that were created ages ago in which the call numbers play a vital part. The problem being that it’s something that’s proven too useful to abandon, and which is hell to update, leaving us stuck more often than not with the way things are because it’s easier than fixing the problems.
And this is a mistake we’re still making, it drives me nuts every time we have another book rebound and get the call number printed on the spine. Look, mistakes happen, classification schemes change (we’re up to Dewey volume 22 after all and it still doesn’t work very well for computers), and collections get moved. It’s all part of the job, but it’s a part we keep forgeting to plan for.