Wikipedia reports that the Great Cameo of France, a five-layered sardonyx cameo measuring 31 cm by 26.5 cm, was created about AD 23.
But what scene does it portray? You can read Wikipedia's somewhat different take, but Anthony A. Barrett, in his biography of the emperor Caligula, argues that it may commemorate the departure of Caligula's father, Germanicus, in the autumn of AD 17 on an important diplomatic mission to the Roman East at the direction of the emperor Tiberius. "According to this view the central figure is the enthroned Tiberius, who bestows the task on Germanicus, who faces him, accoutred in battle armor. Behind Germanicus [on the left] stand [his wife] Agrippina and [his son] the young Caligula."
Germanicus never returned to Italy. He died in Antioch on October 10, AD 19, at the age of 33 years.