This is number 12 of 25 copies signed by Gibbons with a full-page drawing.

Likely the smallest limitation of any Watchmen collectible.

There were three versions of the Dave Gibbons Watchmen Artifact Edition: a regular edition, a Variant Cover Edition limited to 250 copies sold at the IDW booth at San Diego Comic-Con 2014, and "An Evening with Dave Gibbons" Variant Edition limited to 25 signed & numbered copies for collectors attending a dinner with Dave Gibbons at San Diego Comic-Con 2014.

The color illustrated limitation page states:

IDW Publishing Presents An Evening With Dave Gibbons.
Featuring an Exclusive Version of the Dave Gibbons Watchmen Artifact Edition.
Strictly Limited to 25 copies, Signed by the Artist.
Thursday, July 24, 2014

This is number 12 of 25

Opposite the limitation page, Gibbons has drawn a full-page portrait of the Comedian.

The story from Bleeding Cool News:

IDW have published the Watchmen Artifact Edition, reprinting selected pages from the mist celebrated graphic novel of all time, Watchmen, in a fashion that resembles the original art as closely as possible.

But at San Diego, they will be creating an exclusive version that will number 25 copies. And that's all there will ever be. With an exclusive variant painted Rorschach cover by Watchmen's co- creator Dave Gibbons. And just enough copies to fit round a table in a private dining room in a premier restaurant in the Gaslamp area of San Diego, minutes from the Convention Center.

Because that's what's happening. A steak dinner with Dave Gibbons, who will sign and sketch in each and every copy for the folk who have pre-ordered the book, only available at this event.