Harleian Ms6163 Emperour of Constantynenople arms
Depiction of the coat of arms of the "Emperour of Constantynenople" (i.e. ruler of Byzantine empire), in the probable 15th-century manuscript Harley 6163 from the Harleian collection of the British Library.
Reproduced from Two Tudor Books of Arms: Harleian Mss. Nos. 2169 & 6163, with Nine Hundred Illustrations. / A Tudor Book of Arms: Being Harleian Manuscript No. 6163 Blasoned by Joseph Foster, Hon M.A. Oxon, where it is given the following description:
Folio 1.
EMPEROUR OF CONSTANTYNENOPLE.
Gules, a cross between four fire steels reversed or; suggestive of the letter B reversed, the initial of Byzantium. See Harl. MSS. 437, f.48b (1).
However, Byzantines were not calling themselves "Byzantines" but Romans, so a probable suggestion for the 4 Bs is "Βασιλεύς Βασιλέων Βασιλεύων Βασιλεύουσιν" (= King of Kings, Reigning over Kings) en:Palaiologos