From Halopedia, the Halo wiki
The shield is featured as the background shield found on the difficulty emblems for Easy, Normal, Heroic and Legendary difficulties in all currently-released Halo games. It is given some in-universe flavour text in the menus for Halo 2's PC port alongside the Machete. In the Bungie-era Halo games, the shield was emblazoned with the Marathon symbol, though following the transition to Halo 4 and 343 Industries, the shield now features the Reclaimer symbol.
List of appearances