It is a necklace given to the player by Vulpes Inculta (or Alerio, if Vulpes was killed) upon exiting The Tops Casino after completing Ring-a-Ding-Ding! as part of the quest Render Unto Caesar. The Mark allows safe passage to Caesar's camp, even if the player has a low reputation with Caesar's Legion.
- The Mark of Caesar effectively removes all of the Courier's infamy. For example, if the Courier had a reputation of Wild Child prior to receiving the Mark of Caesar, they would now be Idolized among Caesar's Legion.
- Being a quest item, the Mark of Caesar cannot be dropped, even if the Courier sides with the New California Republic in the Second Battle of Hoover Dam.
- Caesar's Legion may still be hostile towards the player even while carrying the Mark. This occurs if the player travels with a companion that is hostile towards the Legion.
- They will also be hostile if you are wearing a hostile faction's clothing while wearing the Mark of Caesar.
- Attacking Legionaries, or otherwise gaining Caesar's Legion infamy, will result in the failure of the quest Render Unto Caesar, despite holding the Mark.
- Attacking Vulpes Inculta or Alerio when either of them gives you the Mark will result in the Legion becoming permanently hostile.
- This item is identical in appearance to the Legion Denarius.
- If the player uses setquestobject 001374ae 0 on the Mark of Caesar and dropped, it will look like a holotape.
- It is possible to gain two of these. By fast-travelling after leaving the Tops, you will have one added to your inventory; then go back to the Strip and talk to Vulpes or Alerio, and they will give you one more.
- pc You can get a second mark when leaving The Fort.