RR-03AW Optio with White Shield, Roman Army of the Late Republic
By the first decades of the 1st century, the COHORT had replaced the maniple as the standard tactical unit of the legions.
The three lines of the manipular legion were combined to form the cohort, which generally numbered about 480 to 500 men. Maniples and centuries continued to be used as military and administrative subdivisions for the cohort. There were six centuries in a cohort, which were now all 80-men strong.
Each Centuria was commanded by a Centurion, and also included an Optio, a Signifer and a Cornicen.
An Optio was an officer appointed by the centurion, and was stationed at the rear of the centuria to keep the troops in order. Their duties would include enforcing the orders of the centurion, taking over the centurion’s command in battle should the need arise, supervising his subordinates, and a variety of administration duties. Optio pay was double the standard legionary pay and they were the most likely men to replace the centurion if the position became vacant.
A Centurion at this time can be distinguished from other Legionaries by several methods. He usually wore greaves, and the crest of his helmet was usually turned so it ran transversely across the helmet. His sword was worn on the left and his dagger on the right which is the opposite of a Legionaire.