A sketch by Perrot showing that it is impossible to change the first letter of the inscription from C to M, 1840

Séguier's interpretation was the subject of discussion in the 19th and 20th centuries. Dating the monument as second century AD, Auguste Pelet identified the Princes of Youth as Marcus Aurelius and Lucius Verus by changing the first letter of the inscription from C to M. This was followed by a bitter argument between the inspector of historic monuments and Perrot the antiquarian.

In 1919, Émile Espérandieu put forward the hypothesis that there had been two successive inscriptions. As Séguier's version did not use all the cramp holes, the first inscription concerned the building of the monument by Agrippa in BC 16. Robert Amy refuted this conjecture, showing that most of the unused cramp holes were to correct clumsy positioning of letters.