Emperor Augustus wore a signet ring with his own likeness on his finger. His successors continued the tradition, wearing it on their fingers as a memento of the great ruler. The exception was Galba, who wore a signet ring on his finger showing a dog peeking out from the bow of a ship. This emperor changed the custom because he had an extremely devoted dog.
The proof of this was the fact that the ruler’s pet in the last minutes of his life protected the ruler from murderers. It should be added that he apparently did it so aggressively that they had to kill the animal first to be able to get to Galba, which was then beheaded.