In 1208-1209, Mahmud conferred a "chatr" (ceremonial parasol) on Aibak, and issued a deed of investiture recognizing him as the ruler of Hindustan. He may have also issued a deed of manumission for Aibak at this time. According to Minhaj's "Tabaqat-i Nasiri", Mahmud styled Aibak as a "Sultan"; chronicler Hasan Nizami also calls him a "Sultan". Nizami states that the "khutba" was read and coins were struck in Aibak's name, but no other source corroborates this claim. No coins issued by him have been found, and no extant coins describe him as a "Sultan".