But problem is we dont really know what that flag is. It is just guessed it could be military flag because of triangle shape. In other hand, all flags then were military, IE, they main purpose was to be carried in front of army in war.

To say. Until the advent of civilian flag at sea, on land used exclusively or military standards or royal and noble banners, to the early 19th century.

Da to kažem. Sve do pojave civilnih zastava na moru, na kopnu se koriste isključivo ili vojni standardi ili vladarski i plemićki baneri, do početka 19 vijeka.