The Civic Crown was a military decoration during the Roman Republic and the subsequent Roman Empire, given to Romans who saved the lives of fellow citizens. It was regarded as the second highest decor
Augustus wearing the oak-leaf Civic Crown, (Glyptothek, Munich)
A diadem was an ornamental headband, and later became a metal crown, worn by monarchs and others as a badge of royalty.
Civic Crown
…Naval crown Diadem Rich, Anthony (1875). "Corona". In Smith, William (ed.). A Dictionary of Greek and Roman Antiquities. London: John Murray. pp. 359–363…
Coin of Antiochus III the Great of the Seleucid Empire, shown wearing a diadem, which was a type of headband tied around the head. Greek inscription reads ΒΑΣΙΛΕΩΣ ΑΝΤΙΟΧΟΥ, "of King Antiochus".
Gold and silver diadem of Philip II of Macedonia. This is one type of diadem used by Macedonian and Hellenistic rulers.
Gold diadem. Greek, probably made in Alexandria, Egypt, and belonging to a noblewoman of the Ptolemaic dynasty (220–100 BC): the clasp is shaped as a Herakles knot
Gold diadem. India, 9th–10th century