What is the treasure mentioned in the Hadith, and does the East mentioned therein mean Khorasan?

The Hadith narrated in Sunan Ibn Majah from Thawban (may Allah be pleased with him) is authentic. It mentions three individuals fighting over a treasure at the Holy Kaaba, followed by the emergence of black banners from the East, engaging in intense combat. The Hadith concludes by stating the obligation to pledge allegiance to Allah's Caliph, the Mahdi, upon his appearance. However, the specification of the black banners originating from Khorasan has not been established in authentic Hadiths, and the Hadith narrated concerning this is weak in its chain of narration.