This is a thick circular lid (or, less likely, a token) worn to a disc shape from a fragment of a thick-walled redware pottery vessel that fired black in some areas.
From Kerma. 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 19, 2006)
Harvard University–Boston Museum of Fine Arts Expedition