Phalearae on Standards

[M. CVRIVS ALEXANDER]

So here's the list of what we know so far:
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2. Cohorts (although we know that they had some kind of distinctive that was visually recognized, e.g., the infiltrators during a civil war who entered the enemy camp by using purloined shields) may not have had standards anyhow, nor did centuries have their own.
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4. The command "Ad Signa" would be meaningless unless there were signa placed somewhere around which to rally. Seems reasonable that there would be enough that any soldier anywhere on the field could find one to move toward. (Lots of sources, of course, but no need to list any of them here, right?)

2. Each century had its signum.
4. Every soldier would rally to his century's signum.