Chief EG-X
From Halopedia, the Halo Wiki
In Halo 3, if you play a multiplayer match, and then fire a bullet and pause the video afterwards, fly over to the casing, and look at the back of it. It says Chief EG-X. Sometimes small patterns can be seen. This is on the Battle Rifle, Assault Rifle, Pistol, Sniper Rifle, and Machine Gun Turret.
