It is a necklace given to the player character 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 character even while carrying the Mark. This occurs if the player character travels with a companion that is hostile (such as Boone) towards the Legion.
- They will also be hostile if the Courier is wearing a hostile faction's clothing (for example, NCR armor) 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 the Mark will result in the Legion becoming permanently hostile.
- The Mark's inventory icon is identical in appearance to the Legion Denarius, with the exception of the ring swivel and attached string to make it a necklace.
- If the console setquestobject 001374ae 0 is used on the Mark of Caesar to remove the quest item state, when dropped, it will look like a holodisk.
- It is possible to gain two of these. By fast-traveling after leaving the Tops, another will be added to the inventory. Returning to the Strip and talking to Vulpes or Alerio will result in them giving one more.
- Ambassador Crocker's note has the same purpose, as receiving it from Dennis Crocker removes any negative reputation for the NCR.
- The Fort. [verified] You can get a second mark when leaving
- It is possible for the player's reputation to decline after receiving the Mark. For example, if the Courier had an Idolized reputation with the NCR, it could become Wild Child after receiving the Mark. Members of the NCR may also be hostile towards the Courier for seemingly no reason, even while wearing NCR faction armor, once the Courier receives the Mark. [verified]