This is a disc-shaped lid made of a redware/blackware clay fabric. It is very well shaped. It is likely that it was fashioned deliberately as a lid rather than from a fragment of a pottery vessel (as some were).
From Kerma, Cemetery S, grave 2200. 1914: excavated by the Harvard University–Boston Museum of Fine Arts Expedition; assigned to the MFA in the division of finds by the government of the Sudan. (Accession Date: September 18, 2006)
Harvard University–Boston Museum of Fine Arts Expedition