If the well-known SATOR word square (a cryptogram of doubtful interpretation) is Christian, the examples of it found at Pompeii (destroyed in 79) must be the earliest extant Christian inscriptions. 3rd-cent. inscriptions are fairly common in the Roman catacombs and from the 4th cent. they are very common in Rome, N. Africa, Syria, and Asia Minor.
In contrast to pagan inscriptions, Christian inscriptions give little personal detail. They are valuable en masse as evidence of the texture of the community and the expansion of the Church, and bear witness to the beliefs of rank-and-file Christians of the period.