Quote Originally Posted by licence View Post
After you get Rank S, I believe you are given Excalibur from Giglamesh.
No, Excalibur is found in Daguerreo I believe, but it's not to do with Gilgamesh. Getting Rank S gets you a Key Item saying you're a Master Treasure Hunter or something, and Gilgamesh (who is unnamed at that point) tells you his name.