 However, the rough finish on the interior stonework leads many scholars to believe that the frescoes were added as part of the original building programme.A "terminus ante quem" was provided by the discovery of graffiti scratched into the fresco plaster recording a number of clerical appointments, the earliest of which is dated (by the name of the presiding Archbishop of Milan) to 948 at the latest.Many writers feel that a certain interval must have elapsed after the painting of the cycle before the clergy would have treated the paintings in this way.