Speculatores

[M. Caecilius]

So could the full text run as follows?

"M. Staberius,(centurio) COH(ortis) VI SPECULAT(or)CLAS(sis) MISEN(ensis)"

I would say so, yes.

Interesting career, though. From speculator in the rather little-respected navy to centurio in the most prestigious unit, with no other service in between that he cares to mention. That appears to be quite a career jump. Did our spy find out something? Speculator with a praetorian Cohort VI and then centurio in the Misenum Fleet would sound less strange, but short of assuming an error on the in/transcription (which is the very last resort and should be avoided), there's no way I see to have the inscription say that.

It also seems interesting that he bears the same nomen as his mother, and a fairly rare nomen at that (the Epigraphy Databank knows only one member of that gens, in Numidia). There's a few ideas that would cross the mind (father unknown; both are freed slaves and he got citizenship after his navy service) beyond his father having married someone from the same gens but that's pure speculation.

I wonder what has become of the inscription. As said, the Epigraphy Databank does not feature it, but if someone could find it in CIL, that might be useful.