About A.D. 106 Pliny appeared against the Bithynians for the proconsul Varenus Rufus (Ep. vi. 29, 11).
From 111-2 or 112-3 A.D. Pliny was governor of Pontus and Bithynia, being sent out for a special purpose by the emperor as legatus pro praetore consulari potestate. Cf. the chief inscription (below) and the words of Trajan.
Trai. 32, ‘Meminerimus idcirco te in istam provinciam missum, quoniam multa in ea emendanda apparuerint.’
The date of Pliny’s governorship is fixed by the mention of Calpurnius Macer in the letters (ad Trai. 42; 61; 62) as the governor of the nearest province. Mommsen has identified him with P. Calpurnius Macer Caulius Rufus, who is shown by an inscription (C.I.L. iii. 7 and 17) to have been governor of Lower Moesia in 112 A.D. This is corroborated by the fact that no mention is made of Bithynia in the chief collection of letters, which was not completed till A.D. 108 at least. Therefore the governorship falls after that time. On the other hand, Pliny must have been sent out not later than A.D. 113, as in the chief inscription Optimus does not appear in Trajan’s name, and this cognomen he assumed in A.D. 114. Finally, the fact that Trajan was at Rome during Pliny’s governorship points to a time between the end of the second Dacian War in A.D. 107 and the outbreak of the Parthian War in A.D. 113.
Our information about Pliny ends with the close of his correspondence with Trajan. It is certain that he held no further office, and it is probable that he died before A.D. 114 in his province or shortly after his return to Rome.
As regards municipal relations, Pliny held the post of flamen divi Augusti, according to the inscription which the corporation of Vercellae erected to him at his own town (C.I.L. v. 5667).
‘C. Plini[o L. f. O]uf. Caec[ilio] Secundo [c]os. augur. cur. alv. Tib. [et ripa]r. et cloac. urb. [praef. a]er. Sat. praef. aer. mil. [pr. tr. pl.] imp. sevir. eq. R. tr. ml. leg. iii. Gall. x. viro stl. iud. fl. divi T. Aug.’
For bequests to his native town see the chief inscription (below). Besides these are mentioned gifts in his life-time. Under Domitian Pliny presented his townspeople with a library (Ep. i, 8), apparently worth 1,000,000 sesterces (v. 7), and endowed it with 100,000 sesterces. He also gave 500,000 sesterces for the support of freeborn boys and girls (Ep. i, 8); and promised to pay one-third of the salary of the professor of rhetoric at Comum (Ep. iv. 13, 5).
The following is the chief inscription of Pliny (as restored by Mommsen), which was erected at the Thermae which he presented to Comum (C.I.L. v. 5262):
‘C. Plinius L. f. Ouf. Caecilius Secundus cos. augur legat. pro pr. provinciae Ponti et Bithyniae consulari potestat. in eam provinciam ex. s. c. missus ab Imp. Caesar. Nerva Traiano Aug. Germanico Dacico p.p. curator alvei Tiberis et riparum et cloacar. urb. praef. aerari Saturni praef. aerari milit. pr. trib. pl. quaestor imp. sevir equitum Romanorum trib. milit. leg. iii. Gallicae x.vir stlitib. iudicand. thermas ex HS ... adiectis in ornatum HS ccc ... et eo amplius in tutelam HS CC t. f. i. item in alimenta libertor. suorum homin. C. HS XVIII LXVI DCLXVI reip. legavit, quorum increment. postea ad epulum pleb. urban. voluit pertinere ... item vivus dedit in aliment. pueror. et puellar. pleb. urban. HS D item bybliothecam et in tutelam bybliothecae HS C.’