This is a lid (or, less likely, a token) shaped from a fragment of a blackware pottery vessel that has been worn down into a disc shape. It may have been used for an offering/model vessel.
From Kerma, Cemetery S. 1913: 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