The flag of the Shah Tahmasp I King of Persia in the 16th century.

• WARNING: Amateur Web source "Image taken from the 1771 Encyclopedia Britannica: on a green field a golden sheep standing before the rising sun. This flag has been used for 5 decades during the rule of Shah Tahmasb of Persia (1524 -1576). The reason he had placed a sheep on the official flag, was that because he was born during the month of Aries, and the symbol of that month is a ram. After Shah Tahmasb's death, the sheep was replaced by a lion again." [1]
• WARNING: This flag only seems to appear in Encyclopedia Britannica 1771 (p.604 plate LXXXI). The corresponding text only explains that these are naval flags anyway: "FLAG is more particularly used at sea; for the colours, ancients, standards, etc. borne on the top of the masts of vessels, to notify the person who commands the ship, of what nation it is, and whether it be equipped for war or trade, fee Plate LXXXI.", and there is no reference to Shah Tahmasp either (p.598)
• Only possible hint: a painting of Shah Abbas and Jahangir showing Shah Abbas standing on a lamb (facing Jahangir's "lion"), but this might just be a taunt.