Picture is courtesy of "phool 4 XC" who published it on Flickr.
This is the first time I stumble upon a Coptic six-pointed star.
The Mystery Of The Menorah And The Star Richard A. Freund University of Hartford in
Nationalism, Zionism and ethnic mobilization of the Jews in 1900 and beyond ed. Michael Berkowitz, 2004 ISBN 9004131841 :
Coptic Christianity also picked up the symbol and used it on stamps with a cross in the center, a rosette in the center, and with a series of triangles in and around the points of the hexagram