Double-headed eagles have been present in imagery for many centuries. The two-headed eagle can be found in archaeological remains of the Hittite civilization dating from a period that ranges from the 20th century BC to the 13th century BC.
Cylindric seals discovered in Bogazkoy, an old Hittite capital in modern-day Turkey, represent clearly a two-headed eagle with spread wings. The aesthetics of this symmetrical position explains in part the birth of this religious figure. It probably dates from the 18th century BC, and was used in a tradesman background. It can also be seen in the same region in two monumental settings: in Alacahöyük around 1400 BC and in Yazilikaya before 1250 BC. Here the context looks different and totally religious: the eagle becomes a divinity symbol. The two-headed eagle slowly disappears during the last Hittite period, from the 9th century BC to the 7th century BC, and totally disappears after the end of the empire.Found Here: http://en.wikipedia.org/wiki/Double-headed_eagle