"Every farmer, every laborer, every fisherman can both read and write — and we think that books instead of being locked up in cupboards, far from the sight of students, should be distributed as widely as possible. The books of our library are therefore
passed from hand to hand without returning to the library shelves perhaps for years."
The pre-numbered labels have not been restored yet since the new site went live at the end of May. You can still request pre-numbered numbers, though, in 10s or 100s, but you'll have to write them on a label yourself. There are a lot of links to great user-generated labels in this thread: http://www.bookcrossing.com/forum/7/358601. I believe JamesUK has some labels on his site that will number the labels for you.