The Dedicatory Inscription of the Aqua Claudia

The Porta Maggiore at Rome is a monumental gate formed by the arches of two aqueducts, the Aqua Claudia and the Anio Novus, where they crossed two roads. One of its inscriptions states that Claudius brought both waters into the city at his own expense. It gives his titles: tribunician power for the twelfth time, consul for the fifth time, imperator for the twenty-seventh time.

It matters here only for the count of acclamations. Gaius was killed on 24 January 41 and Claudius was accepted as emperor the next day (Suetonius, Caligula 58; Claudius 10), so his twelfth year of tribunician power ran from January 52 to January 53. A letter of his at Delphi, the Gallio Inscription from Delphi, was written when he had been acclaimed imperator twenty-six times, and so no later than that year.