Legionum Insignia. Most of the insignia of the legions may be seen on the silver coins of Gallienus. As the legion was composed of hastati, principes, and legionarii, even after the form of the Militia Romana was changed by C. Marius, so there are to be observed on denarii of the Claudia family, and others, three military ensigns; the first of which may denote the Hastati, that is to say, those who formed the first line of the army, carrying spears; another, the Principes, who formed the second line of battle array, and were of a more robust age; and the third the eagle of the legionarii placed in the middle, between the two above mentioned. Upon a second brass of Galba
are three military standards, which, from being mounted on prows of galleys, denote the two services, the army and the navy.
The eagle is the special symbol of the legions [and of Zeus / Jupiter]. The legions were divided into cohorts, maniples, and centuries. To the second of these the hand, manus, which is often seen upon some of the standards may apply.