COH - stands for cohort as in a unit of a Roman legion. It was usually how a military banner would start.

SPECVL - Stands for Speculatores. Which were a section of the Roman army that were responsible for law-enforcement. At first they were scouts but they grew in importance and by the time of Spartacus they were also used as bodyguards to political figures (such as Praetors like Glaber).

OPTIMA - Is the plural form of optimum, which basically means best.

FELIX - Simply means lucky. Or Luck.