and their successor states. In Byzantine heraldry, the heads represent the Emperor having authority over both secular and religious matters, Byzantine emperors were regarded as Christ's viceregent on Earth. It also signified the dominance of the Byzantine Emperors over both East and West.

http://en.wikipedia.org/wiki/Double-headed_eagle


не нашел информации о гербе Золотой Орды, но флаг у них был такой:



http://en.wikipedia.org/wiki/Golden_Horde