This is my entry for the latest flag challenge on ah.com:[link]
It is the standard of the Grand Prince Commander of Narangeaux-Leones.
The title Grand Prince was given to the Prince of Narangeaux by the Holy Francian Emperor in 1469.The title of Commander was the original title of the ruler of OTL Genua. In 1701 the titles were combined for eternity, making it one of the most unusual noble title in Europe.
Narangeaux = OTL Orange, France
Leones = ATL Italian Noble House