Ivlivs

Ivlivs is a coin belonging to Jason Grace that, when flipped, turns into a double edged sword or a lance, depending on which side the coin lands on. The sword side has an image of Julius Caesar, while the lance side has an axe and the word "Ivlivs". It is made from Imperial Gold, which must be concecrated in the Temple of Jupiter on the Capitoline Hill in Rome, therefore making it very rare. It is possible that the inscription is supposed to say "Julius" since in Latin "J" is generally pronounced as "I". This metal is mentioned as very volatile, which is proven when Jason breaks his lance in combat and it creates a massize crater. It is possible that Imperial Gold can kill storm spirits even when they are aware. It was destroyed by Enceladus when he fought Jason at Mount Diablo.

Trivia

 * ﻿Ivlivs would actually be called "Julius" because in Roman times a "U" was represented by a "V", and there was no J in latin so the letter I replaced it.
 * The coin's two sides have Julius Caesar on one and an axe on the other, which refers to Caesar's victorius conquest over the barbarian tribes of Gaul (France) which were represented by an axe.