Brought to my attention by Dorothy King the PhDiva: “A fourth century BC sword may have the oldest known inscription of the name of Rome.”
The inscription reads: TR POMPONIO(S) C (f.?) (M)E FECET ROMA(I). The letters in parentheses are supplied by the excavators, since often Latin inscriptions could leave out parts of words and endings. They reconstruct it as: “Trebius Pomponius, son of Gaius, made me in Rome”. Presumably the “ROMAI” they supply is in the locative case, which would be “AE” normally but was “AI” in Old Latin (or so JSTOR tells me)
The sword was found in 2003 in the excavations of a water cult sanctuary near San Vittore del Lazio (southern Lazio). The excavators claim it is similar to swords used in the La Tène B2 period. (Notice posted in Italian)
The sword is mainly dated by the Macedonian star decorations. Another very early inscription that records it was made “ROMAI” is the famous Ficoroni Cista. It also possibly dates to the 4th century BCE. If both can be considered products of Archaic Rome (having recovered from the 5th century economic crisis), they are important archaeological evidence that the settlement on the Tiber called itself Rome.