This is one of the Artist's Proofs sold by Stan directly to his fans at conventions.
"This is number 21AP of 500 copies of the hardcover edition ... each of which has been individually signed, numbered, and illustrated by Stan Sakai." It has a bound-in limitation page with a 4 inch square where Stan has drawn a full scene with Usagi and a tokage with clouds in the distance.
Volume 11 collects issues 7-12 of the Dark Horse comic book series Usagi Yojimbo Volume Three, and Colour Special #4, and plus a cover gallery. Introduction by Lynn Johnston.
From the publisher:
Spring breezes stirring the memories of lost battles. Summer fields burning with fires of treachery. Chill autumn nights echoing with demonic screams. Winter snows stained red with the blood of honor. Follow Stan Sakai's Eisner award-winning Usagi Yojimbo through a cycle of short stories continuing the ronin rabbit's journeys through feudal Japan. Ten tales in all, an essential collection for all seasons!