RR-03BR Optio, 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.