I bought this book in 1986 when it came out and put the cover on the dust jacket the same day as I did with all of my King books. It is both a first edition and the first run in the first edition - no date under the Garamond No. 3 line

Stored dark all these years.

Smoke free home.

“as the first time a publisher ever underestimated the number of books they would need to satisfy the demand. They really thought 400,000 would accommodate the supply and they weren't prepared for the bookseller market to demand more copies. IT, more than any other Stephen King novel, changed the number of first printing editions that Viking produced

400,000 initial 1st print run:

There will be nothing stated on the CP page under the Garamond 3 line. This run was produced the week of August

100,000 combined 2nd and 3rd print run:

Second Printing - August 1986 on the copyright page under the Garamond 3 line, to indicate this was produced the week of August 25, 1986

Third Printing - September 1986 on the copyright page under the Garamond 3 line, to indicate this was produced the week of September 1, 1986

300,000 combined 4th and 5th print run:

Fourth Printing - September 1986 on the copyright page under the Garamond 3 line, to indicate this was produced the week of September 8, 1986

Fifth Printing - September 1986 on the copyright page under the Garamond 3 line, to indicate this was produced the week of September 15, 1986 (and the actual week of publication)

All five of these states were released simultaneously on the date of publication. They are all considered First Editions. The First Printing is the largest printing. The Second and Third stated printings are the smallest printings. The fourth and fifth printings are not as common as the unstated first printing, but are more common than the second and third printings.

Since most collectors are interested in 1st edition / 1st printings the 400,000 run would generally be considered the most collectible even if it's not the rarest.”