Upon the triumphal arches, the altars, and the coins of Rome, SPQR stood for Senatus Populusque Romanus (the Senate and the Roman people). In antiquity, it was a shorthand means of signifying the entirety of the Roman state by referencing its two component parts: Rome's Senate and her people.
In the time of the Roman Republic the Standards were imprinted with the letters SPQR which was an abbreviation for Senatus Populusque Romanus (Senate and People of Rome). The Standard, then, represented not only the legion or cohort which carried it but the citizens of Rome, and the policies the army represented.
