Nope, that is a label that should have been stuck to a priority mail box (The piece of mail, not the box that is attached to the ground). Someone wrote "Bukowski" and stuck the label to the metal box.
It's almost like a tribute plaque. Sort of "To Bukowski, for his years of service to the U. S. Postal Service." Funny that it hasn't been scraped off yet by some postal worker. Maybe they read him.