Number line (printer’s key)
The row of numbers on a book’s copyright page is the number line, or printer’s key. It counts printings: the lowest number left in the line is usually the printing a copy comes from, so a line with a 1 in it marks a first printing.
How to read it
The University of Chicago Press calls it the impression line. For each new printing the printer masks the lowest number, so the copyright page shows the change without being typeset again. The Independent Online Booksellers Association (IOBA) gives the forms it takes: 1 2 3 4 5 6 7 8 9 in order, 1 3 5 7 9 8 6 4 2 alternating, 10 9 8 7 6 5 4 3 2 1 in reverse, or letters, A B C D E, where A marks the first. Whatever the order, the 1 or the A is the first printing; a line whose lowest number is 2 is probably the second. The order says nothing about which printing it is: 10 9 8 7 6 5 4 3 2 1 and 1 2 3 4 5 6 7 8 9 both mark a first printing.
Also searched as: first edition number line, first printing, how to tell if a book is a first edition, number line, printer’s key, printers key.
This page says what the marks in a book mean, from publishers’ and librarians’ own accounts. Publishers’ practices differ; it doesn’t identify or value any copy.
Lines with years in them
The University of Chicago Press puts two groups of numbers in its own books: years, then printings. Its example, for a book first printed in 2005, is 14 13 12 11 10 09 08 07 06 05 1 2 3 4 5: the first printing, in 2005. For a second printing in 2007 the printer masks 05 and 06 and the 1, leaving 14 13 12 11 10 09 08 07 2 3 4 5.
Random House and the line that starts at 2
IOBA records that Random House, until roughly 2003, printed the words First Edition in place of the number 1. On a Random House book from before about 2003, a First Edition statement above a line starting at 2 is the first printing.
A printing is not an edition
The number line counts printings, which the trade also calls impressions. The Antiquarian Booksellers’ Association of America (ABAA) defines an edition as all the copies printed from the same plates or setting of type, and a printing as the copies from one press run. A second printing from unchanged type is still the first edition in that strict sense. Collectors mean something narrower: in John Carter and Nicolas Barker’s ABC for Book Collectors, “first edition”, unless qualified, is taken to mean the first impression of the first edition.
When the line doesn’t match the book
IOBA lists exceptions. The 1 stayed in the number line of the Lemony Snicket books even as the price on the back cover went up. The first US printing of Jeanette Winterson’s Oranges Are Not the Only Fruit, a trade paperback, has no number line at all, though at least three printings say “first”. For any one author, IOBA names the descriptive bibliography as the most definitive record of which printing is which.
Read next
- Next in First edition and book club marksFirst edition statementWords such as “First Edition” or “First Printing” on the back of the title page are the publisher’s statement of edition. Publishers and collectors use “first edition” in different senses, so the words don’t settle which printing a copy is.
- The same shape in AI labels and iconsContent Credentials (CR) iconContent Credentials. The small CR pin on an image or video means the file carries Content Credentials: signed information about how it was made and edited, which can include whether AI tools were used. Selecting the pin shows the details.
More first edition and book club marks
The same shape elsewhere
Browse symbols drawn with letters and numbers or squares and rectangles.
Sources
- Impression line (Chicago Manual of Style Online, Q&A), The Chicago Manual of Style Online, Questions and Answers: Manuscript Preparation, Copyediting, and Proofreading, University of Chicago Press, Q&A, Manuscript Preparation
- Identifying First Editions, A Primer: In General (IOBA), Independent Online Booksellers Association, “Identifying First Editions, A Primer: In General”, Part I, Independent Online Booksellers Association, “Numbers on books help identify first editions”; “A brief list of often misidentified modern first editions”; Introduction
- Edition & Printing (ABAA Glossary of Terms), ABAA Glossary of Terms, “Edition & Printing”, Antiquarian Booksellers’ Association of America, Definition
- ABC for Book Collectors, by John Carter and Nicolas Barker, John Carter and Nicolas Barker, ABC for Book Collectors, 8th edition (Oak Knoll Press and the British Library, 2004; reprint with corrections 2006), made available by ILAB with Oak Knoll Press’s permission, Oak Knoll Press and the British Library, via the International League of Antiquarian Booksellers, “Edition and impression”, pp. 87–88
Last reviewed October 8, 2026 by Rory Hansen. How we research
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