Coat of Arms of the Ecumenical Patriarchate Constantinople as found on the wall of the St. George's Cathedral, Istanbul, above the entrance. It is described by the Ecumenical Patriarchate on its official website as "the eternal symbol of the Patriarchate, the double-headed eagle" (source) and "an all-round double-headed eagle, the emblem of the Ecumenical Patriarchate and a symbol of the hopes of the Nation, which goes back to the Byzantine imperial symbolism" (source). It is used as an illustration for the EP on its official website's home page. The meaning of the Greek letters ΟΙΚ Π and Κ Π are not indicated, but they probably mean Οικουμενικό Πατριαρχείο (Ecumenical Patriarchate) and Κωνσταντινουπόλεως (of Constantinople).
This version is more faithful than File:CoA of the Ecumenical Patriarchate Constantinople (St. George's Cathedral of Istanbul version).png to the original model.
Own work
This file was derived from:

 CoA of the Ecumenical Patriarchate Constantinople (St. George's Cathedral of Istanbul version).png
Byzantine eagle - emblem of the Ecumenical Patriarchate of Constantinople, entrance of the St. George's Cathedral, Istanbul.jpg
Royal Crown of Denmark.svg
Church of St. George, Istanbul (August 2010).jpg
https://ec-patr.org/wp-content/uploads/2019/10/dikefalos.pngInformation from:

Veverve
Goran tek-en, following request by and knowledge from Veverve