"Stela D, dedicated on the hotun of the cycle that began with Stela B, was to be the final stone monument of the great king who raised it. Standing at the base of Temple 2, it is the northern stela of the Great Plaza and faces south toward the north stairway of Temple 4. Its eloquent imagery presents 18-Rabbit in the guise of an old god.
...the king wears an actual mask that covers the greater part of his face, with large oval openings left around his eyes and mouth so that the viewer can identify him within his disguise. Baudez (1986:137) remarks that this is a "very undiagnostic mask," although he tentatively believes it represent the old sun god. The mask has the features of an aged face, with prominently sagging jowls, wrinkles that surround the lips, and nearly toothless gums. An oval cartouche that fills the forehead of the mask probably held a mirror sign for brightness. A short, squarish length of beard like that which 18-Rabbit wears on Stela B seems to be part of the mask. The king's hair flares away from his face, falling in long locks just in front of his earspools."
Elizabeth A. Newsome, Trees of Paradise and Pillars of the World: The Serial Stela Cycle of 18-Rabbit-God K, King of Copan, p. 141-3