Current knowledge
Emperor Vitellius (Otto) with wings, sitting asleep leaning on his left hand
This destroyed Emperor series by Titian is known through famous engravings by Aegidius Sadeler II. This particular emperor was a replacement commissioned from Sir Anthony van Dyck
Van der Doort 1639
Titian
Emperor Vitellius with wings, sitting asleep leaning on his left hand
Sale Inventory c.1649-51
Walpole Society reference (1972):