This is an artists proof, done entirely in the ukiyo-e method of Japanese woodblock printing. Each color field is printed from individually carved wood blocks. The blocks are hand-inked with brushes using water-based pigment inks; gradations are rubbed by hand.
It all starts with what's called a "keyblock": the prints black outline(s) are carved into a smooth block of hard maple (in this case, left over ends of stair treds.) Prints are made from the keyblock onto thin, strong "Gampi" paper, and transferred to each anticipated color block.