This is a roughly shaped circular lid (or, less likely, a token) formed from a fragment of a pottery vessel. It may have been used for an offering/model vessel.
From Kerma, Cemetery S, grave 1615. 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