SPQR
It was emblazoned on the standards of the Roman legions. It also appears in the coat of arms of today's city of Rome.
*: Several versions are suggested about the correct meaning of the acronym, depending on the presumed declination of 'R', which can be as well Romanus (Senatus or Populus) or Romani (Senatus and Populus) or Romae (of Rome).