Just to expand, it's Mark V but Halo Infinite's and then slightly updated for Unreal Engine.
Mark V in CE
Mark V in Halo Infinite
Mark V in Unreal Engine 5
Halo 3 Chief is Mark VI
Here's a GEN3 Mark VI Spartan with a GEN1 Mark V Spartan in Infinite.
Technically, it doesn't confirm it is "Halo CE Chief" but it is the version of armour that Halo CE Chief uses.