This is a slightly curving fragment, with part of an incised hieroglyphic inscription reading 'n ka'. It is possibly from a block or cross legged statue. The dark brown stone is very fine grained with no visible inclusions.
From Nubia (Sudan), Kerma, K III 2(1)a. 1914: Excavated by the Harvard University–Boston Museum of Fine Arts Expedition; assigned to the MFA by the government of Sudan.
Harvard University—Boston Museum of Fine Arts Expedition