The number line, or printer's key, often seen on the copyright page of books is simply a
method of record-keeping that helps identify the book's printing and, for some, year of
printing a specific book, which may or may not be different than the original copyright
date listed elsewhere on the page.
Common examples of these number lines include: 1 2 3 4 5 6 7 8 9 10
or 2 3 4 5 6 93 92 91 90
or 3 4 5 6 7 8 9 10 MPC 19 18 17 16
or even 1 3 5 7 9 10 8 6 4 2.
While different publishers use different conventions for these number lines, generally speaking,
the smallest number in the line indicates a books printing.
So if 1 2 3 4 5 6 7 8 9 10 is at the bottom of the page, it is a first printing; if the
number one has been removed, so the number line is 2 3 4 5 6 7 8 9 10, it is a second
printing; and if it's 3 4 5 6 7 8 9 10, it is a third printing, etc.
The reason they remove a number each time instead of, say, just changing one number
has to do with the way publishers have historically printed books.
For instance, in offset printing, you can relatively easily remove something from the
printing plate, but adding a number would require creating a whole new plate.
In any event, sometimes number lines are accompanied by the words First edition but that does not
necessarily mean it is the first printing; for example, this would indicate a third printing
of a first edition: First edition
3 4 5 6 7 8 9 10 There may be many printings of an edition,
the latter of which may be defined as a single "setting-up of type without substantial change."
So, if the author doesn't change the text of the book (like text books authors frequently
do), and the pages all stay the same, then if the publisher simply makes another round
of copies, it isn't a new edition, it's just a new printing.
If, however, the pages are substantially modified, or the book is reformatted, such as for printing
in paperback, then the printings in this new format will be a new edition.
Note, though, that it may not be designated as a second edition (or third or fourth),
and instead may be called a first paperback edition, first US edition or Penguin Classics
first edition.
Serious collectors typically consider these last inferior to the cherished first edition,
first printing.
Depending on the publisher, the number line might also indicate the year the printing
was done, like 2 3 4 5 6 93 92 91 90.
This reveals that this second printing was done in 1990.
Much like with the print run numbers, if the book is printed again the following year,
the 90 would be removed, leaving the year part of the string as 93 92 91.
Moreover, if the publisher contracts with an outside company to do the printing, that
company may be indicated in the number line as well; in this example, the number line
shows Melissa's Printing Company was hired to do a third printing in 2016: 3 4 5 6 7
8 9 10 MPC 19 18 17 16.
In addition, some publishers prefer other kinds of lines; for example, Anness Publishing
uses a number line that alternates its digits as 1 3 5 7 9 10 8 6 4 2, where a second printing
would read 3 5 7 9 10 8 6 4 2, and a fifth printing would look like 5 7 9 10 8 6.
This particular schema is used to keep the number line relatively centered over multiple
print runs.
Further demonstrating the lack of standardization across publishers for the printer's key, the
publishing giant Random House has indicated its first edition, first printing with the
words first edition but with a number line that begins with 2 (as opposed to 1) such
as 23456789; but, it uses this same number, just without the words first edition, to indicate
a second printing Bonus Fact:
Ever wonder why some pages are intentionally left blank?
Well, wonder no more: To begin with, the practise of marking intentionally blank pages some
form of "intentionally blank" goes all the way back to the dawn of automated printing
itself, where mistakes in printing were relatively common.
Like today, the main purpose of marking these pages in this way was simply to make sure
people knew that the blank page wasn't a result of a printing error.
Given this, it's no surprise that you'll almost always only see this text on pages that you
might otherwise think shouldn't be blank given their position in the written work.
This brings us around to the much more interesting question of why any pages are left blank in
the first place.
After all, this is a waste of paper and potentially a lot of money given the print volume of some
tests, pamphlets, books, etc.
As for the first on that list, in timed tests an intentionally blank page is often used
as a shield of sorts to stop wily students from trying to read the next section's questions
before they're supposed to.
To make sure no student is confused about a random blank page in their test, they simply
indicate on the page some form of the somewhat contradictory statement, "This page is intentionally
left blank".
Alternatively, they might put something like "Stop Here" instead, so the student knows
to wait until the next timed section starts and that the page is mostly blank for a reason.
Another reason to include a blank page, particularly in certain official documents, is to avoid
ink from a pen potentially bleeding through to another section of the document.
This is also one of the reasons you may sometimes encounter otherwise blank pages saying something
like "Do not write anything on this page".
In both cases, the page is there simply to prevent processing errors due to ink-bleed.
Blank pages in books and other bound works, on the other hand, are generally there because
these works are often created by folding single, large sheets of paper in very specific ways
and binding them all together.
This group of pages is known as a "signature" and might include something like 4, 8, 16,
or 32 pages out of a single large sheet.
Regardless of how the paper is folded, the end result is going to be a book or booklet
with an even number of pages.
If you look carefully at the spine of a book you have lying around, you may even be able
to see this sort of grouping of pages if you let it flair open a bit.
So, for example, if the content of the book fills 299 pages, the layout artist might choose
a signature of 4- thus a minimum of 75 folded sheets making up 300 total pages, including
one blank page.
On the somewhat extreme end, if the signature comprises 32 pages (so 10 folded sheets making
up 320 pages), you'll have a whopping 21 blank pages, making this signature likely a poor
choice here, though there still might be financial or technical reasons to use it anyway.
Of course, savvy editors or layout artists tend to try to tweak formatting to help the
book fit the chosen signature while minimizing needed pages.
But inevitably there's going to be times where nothing can be done and there will be a blank
page or pages.
In this case, they might resort to tricks such as putting advertisements about some
of the other works by the author or publisher in.
Alternatively, they might put in a short biography on the author, rather than have it somewhere
on the cover.
Or, if necessary, they might move such a biography to the cover to save a page within the book.
Alternatively, they might indicate the blank page(s) are for the reader to take notes,
particularly in works like textbooks.
All of these tricks are basically ways of avoiding a random blank page, or in some cases
needing to put something like "This page is intentionally left blank" in the book.
Nevertheless, you'll still occasionally see this text in some bound works, again in these
cases generally only put there in cases where the editor in question thinks the reader might
think the page was not supposed to be blank.
So, for instance, you may have noticed that many books have a blank page at the start
or end or both; this is a safe bet not to confuse anyone, so is a handy way to mask
that the book's content didn't quite fit the signature without needing to put "This page
intentionally left blank".