In many books, along with the copyright info, I often see a string of numbers, like the following:
1 2 3 4 5 6 7 8
15 14 13 12 11 10 9 8 7 6
1 3 5 7 9 10 8 6 4 2
or letters
B C D E F G H I
Usually they are the final line of text following all the other info. Not all books have them, but many do. What the hell do they mean?
IIRC at least some of the numbers are used to indicate the number of the printing run to which the book belonged. The numbers are written out in sequence: 6 5 4 3 2 1 for the first printing run, and numbers are stricken out as necessary for each successive printing run. The second printing would have 6 5 4 3 2, and so on. The smallest number will be the printing run to which the book belongs. Presumably, it’s easier to erase numbers than to prepare a new page for each printing run.
The letters probably mean the same thing, with A = 1, B = 2, etc. The sequence of odd numbers followed by even numbers works by erasing a number from the left side, then from the right side: 1 3 5 4 2, then 3 5 4 2, then 3 5 4, then 5 4, then 5. This would keep the line of text centered. One of the books I checked does have the sequence of numbers centered, but it goes 10 9 8 7 6. I guess it was printed electronically, but maintains the tradition of using these sequences.
The more serious book collectors use this information because they not only like to collect first editions but a first ( or early ) print run makes all the difference to the value of the book. The only difficulty with this system is that not all publishers put this information in their books.
I have a guidebook (think it’s for Chrono Cross, but don’t quote me on that) that uses this system. The interesting thing is that the number the furthest to the right is 0.