Mark of Caesar

The Mark of Caesar is a miscellaneous item in Fallout: New Vegas.

Characteristics
Given to the player by Caesar's representative upon exiting The Tops Casino after completing Ring-a-Ding-Ding, the Mark of Caesar allows safe passage to Caesar's camp even if the player has a low reputation with Caesar's Legion.

Bugs
Caesar's Legion may still be hostile towards the player, even when carrying the Mark of Caesar. This could be because you have a companion (like Boone) who hates the Legion. I notice this stops once we stop traveling together.