Promotion to the centurionate.

[D B Campbell]

I have made an study about one centurio promoted directly from civil life, being an equites. His name was Lucius Alfenus Avitianus, that i have adopted as nickname.

Interesting. I suppose you mean ILS (Dessau) 367:

Imp(eratori) Caes(ari)
L(ucio) Aurelio
Vero Aug(usto) Ar-
men(ico) Part(hico) m(aximo)
Med(ico) p(ontifici) m(aximo) tr(ibunicia) p(otestate) V
co(n)s(uli) III
L(ucius) Alfenus Avi-
tianus p(rimus) p(ilus) tr(ibunus)
coh(ortis) III vig(ilum)
XII urbana(e)
[...]

May I ask: what makes you think he had a direct commission as centurion?