PRAEFF in the Inscription of L. Artorius Castus is an Error for PRAEF

Professor Roger Tomlin sees PRAEFF of the L. Artorius Castus inscription as a stonecutter's error:

"No difficulty in supposing that Castus was prefect twice. Your difficulty is that he would have said iterum, as often in inscriptions referring to repeated tenure. praeff is common enough, but it refers to 'prefects' (plural), for example officers 'of the praetorian prefects', praeff praetorio.. 

Doubling the final consonant of an abbreviated title or office is so common to indicate a plural - AVGG for two emperors, never an emperor twice – that you will have to find a good instance of its being done in the way you would like, to refer to an office held twice."

I asked him about what seemed a similar use of praeff leggionum in another inscription:

publication: CIL 11, 05216 = IDRE-01, 00122 

dating: 193 to 235 EDCS-ID: EDCS-22901158

province: Umbria / Regio VI place: Foligno / Fulginiae

[P(ublio) Aelio P(ubli) f(ilio) Papir(ia)] / [Ma]rcello [cent(urioni)] / [frum(entariorum) s]ubprincipi pe/[regrino]rum [a]dstato et pr[incipi] / [e]t pri[mo] pilo leg(ionis) VII G[em(inae) Piae] / [Fel(icis) adle]cto ad mu[nera] / praeff(ectorum) le[gg(ionum) V]II Claud(iae) [et] / [prim]ae Adiutricis v(iro) e(gregio) fla[mini] / [Lu]culari Laurent(i) Lav[ina(ti)] / [pa]t[r]ono et decurio[ni coloniae] / [Ap]ule(n)sium pa[trono] / [civitat(ium) Forofla(miniensium) Fulginia(tium)] / [itemque Iguvinorum splendidissimus] [ordo Foroflam(iniensium)] / [cuius dedicat(ione)

inscription genus / personal status: milites; ordo equester; sacerdotes pagani; tituli honorarii; tria nomina; viri

material: lapis

His comment?

"Yes, an interesting parallel, but it doesn't help you with Castus. Marcellus is acting-prefect of two legions in turn, not of the same legion twice. And he does not use PRAEFF to say that he was prefect twice. The abbreviation PRAEFF follows ADLECTO AD MVNERA, meaning that he 'replaced' the two prefects in turn. This PRAEFF for praef(ectorum) is just like the inscriptions I mentioned to you [1], which honour officers 'of the praetorian prefects' (plural). The double FF simply means 'two (or more) prefects'.

Marcellus in his other inscriptions is described as EX PRAEFECTO LEGION and EX PRAEF LEG (followed by the names of the two legions), not as PRAEFF, which is what you need as a parallel."

An extensive search on my part has failed to produce the same usage of PRAEFF as is found in the Castus stone.  For this reason, I personally am satisfied PRAEFF is, indeed, a stonecutter's error. 

As for how the error was made, the most common-sense explanation has to do with the marked similarity of the letters F and E in the inscription.  Quite literally, an F is an E with the lower leg left off.  PRAEFECTUS could be abbreviated in many different ways, including as PRAEFE (see https://www.trismegistos.org/abb/list.php?abb=&abb_type=exact&abb_word=PRAEFECTUS&abb_word_type=exact&abb_length=&abb_size=&freq=&comb=AND&search=Search). So it is likely that the second F was meant to be an E.  When I asked Professor Roger Tomlin about this, he replied:

"I think you are right to suppose some sort of typo, whether by the man who laid out the inscription or the man who cut it. A typo made easier by the similarity of E and F."

[1]

"These are both examples of what I said, two or more officers of the same rank. Marius Maximus is writing to all the tribunes, prefects and acting-commanders of the military units in his province. The second is a dedication by a vicarius acting as the 'deputy' of the praetorian prefects (plural).

No, I don't think PRAEFF can have the force of 'prefect twice'. To a Roman it would mean 'two prefects'.

PRAEFF is such an easy stonecutter's error that I don't like to overload it with the sense that LAC was prefect twice. He would surely have said so, in the way that a primus pilus for the second time is proud of being iterum.

PRAEFF just won't bear the interpretation of 'prefect twice': it is not really Latin, and I some phrase like praefectus iterum or bis praefectus would have been used for a second command with the same title. I am happy with the traditional interpretation that FF is a stonecutter's mistake, like his IM for IN in Britanicianarum. 

I don't know of any instance of the final letter being repeated in this way, to indicate repeated tenure. It will be spelt out, with ITERVM. He would have remained prefect while dux."

publication: AE 1933, 00107 = AE 1934, +00281          EDCS-ID: EDCS-16000544

province: Syria         place: Qual'at as-Salhiyah / Qalat al-Salihiyah / Dura Europos

Marius Maximus tribb(unis) et praeff(ectis) et praepositis nn(umerorum) salutem / quid scripserim Minicio Martiali proc(uratori) Augg(ustorum) nn(ostrorum) / et notum haberetis adplicui opto bene valeatis / ex(emplum) / curae tibi sit quaesturae nn(umerorum) per quos transit Goces / legatus Parthorum missus ad {ad} dd(ominos) nn(ostros) Fortissimos Impp(eratores) / secundum morem xenia ei offerre quid autem in / quoque numero erogaveris scribe mihi / Appadana / D[ur]a / Ed[da]na / Bi[blada]

inscription genus / personal status: milites;  nomen singulare;  ordo equester;  tria nomina;  viri

And here

publication: CIL 08, 22830 = ILTun-01, 00091 = AE 1902, 00058          EDCS-ID: EDCS-24200630

province: Africa proconsularis         place: Sfax / Taparura

[Felicissi]mis beatissimisq[ue temporibus dd(ominorum) nn(ostrorum)] / [Valentinia]ni et Valentis m[aximorum principum] / [3]sta congeries Rup[ium 3] / [agente pro pra]eff(ectis) per Africam [3] / [3] curante [

material: lapis