I realise that is what you're aiming at. Somewhat unrelated: I remember a long time ago you were asking about the symbology of the double headed eagle. Something I just read reminded me of this: basically it represents the Roman God Janus, as well as the "Two Saints John", John the Apostle and John the Baptist.

The earliest use of it as a national symbol I have come across is by the late Byzantine Empire, here.

-Joe.