Centurion Position in Battle

[Nathan Ross]

For my part the numbers... strongly suggest 20 per legion

Inscription CIL VIII, 18050, dated AD203, was dedicated by an optio and 34 cornicines of Legio III Augusta.

That might mean that every other century (more or less) had a cornu, or that only half the legion's cornicines were involved with the dedication (or were present in camp at that point!). Vegetius (2.2) states that the tuba and cornu gave different signals.

(this info comes from the Ross Cowan AW article I mentioned before, btw)