This rectangular bead is dark green with serrated edges. Likely a stylized wedjat eye.
From Egypt, Giza, Avenue G 2, between mastabas G 7210-7220: G 7220 and G 7230-7240: G 7230. 1924 : excavated by the Harvard University–Museum of Fine Arts Expedition; assigned to the MFA in the division of finds by the government of Egypt.
Harvard University—Boston Museum of Fine Arts Expedition