Close-up of a double-headed eagle. Seljuk, 13th century. From the Konya city walls.

The double-headed eagle is a common heraldic symbol. It was already used by the Hittites in the 13th century BC. It is most commonly associated with the Byzantine Empire, the Holy Roman (German) Empire, the Russian Empire 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. In the Holy Roman Empire's heraldry, it represented the church and the state.
The double-headed eagle became the standard of the Great-Seljuk Turks with the crowning of Tuğrul Beg at Mosul in 1058 as "King of the East and the West" and was much used afterwards. The Sultans of Rum, Ala ad-Din Keykubad I (1220–1237) and his son Kaykhusraw II (1237–1246) used the dicephalous eagle in their standards, and the motif was also found on tissues, cut stones, mural squares, and Koran holders.

Correspondent: J.M.Criel, Antwerpen.
Source: (amongst others) Wikipedia .