Rectilinear corner fragment. Dressed on 2 sides that form an edge. Same unusual material surface is dark green gray color often with a crackled texture. All incised marks are very finely executed and very crisp.
From Nubia (Sudan) Gebel Barkal, N503. 1916: excavated by the Harvard University-Museum of Fine Arts Expedition; assigned to the MFA by the government of Sudan.
Harvard University—Boston Museum of Fine Arts Expedition