Pier B portrays the First Pacal. This Pacal never ruled Palenque: he died shortly before he would have inheirated the throne. This caused the kingship to pass to his daughter on October 22, 612: Lady Zac-Kuk was Pacal the Great's mother.
"One remarkable feature of Palenque is the absence of freestanding sculptured monuments. Rather than appearing on stelae or altars, the portraits of Palenque's rulers were either carved on stone panels or modeled in plaster, and then placed on the walls of buildings. Most of these portraits are now fragmentary, but both stone and stucco work were once brightly painted, and many interior walls show traces of these modeled and painted decorations. Fortunately, some of the portraits and most of the hieroglyphic texts carved on stone panels remain largely intact, and these (or skillful casts) can be seen inside several of the site's most prominent buildings."
Robert Sharer, The Ancient Maya, p. 278