Until the late nineteenth century this small portal of Kukub ad-din belonged to a structure, now vanished, named the Masjid ash-Sharif. A modern structure now abuts the badly damaged portal. A plaster inscription once ran across the faces of the fired brick portal recess. The remains of this inscription bear a partial date that identifies construction with the year 1307.
Source:
Donald N. Wilber, The Architecture of Islamic Iran, (New York: Greenwood Press, 1969).