The final renovations to the Hieroglyphic Stairway were made by Ruler 15, named K'ak' Yipyaj Chan K'awil. His portrait, Stela M, stands at the foot of the stairway and was erected on the Period Ending 22.214.171.124.0 (AD 756). "Stela M is now badly weathered and battered because of a damaging fall in antiquity. Originally one of the most graceful and refined stelae, this monument portrays the 15th ruler Smoke Shell."
William L. Fash, Scribes, Warriors and Kings: The City of Copán and the Ancient Maya, p. 139