For anyone who may not be familiar with it, the version on the left is Chief's pre-release design that was shown off at MacWorld 1999, when Halo CE was still being developed as a Mac-exclusive third-person shooter. See the original footage and screencap.

An armor set inspired by the MacWorld design later made it's way into the Master Chief Collection as the Orion set for Halo 2 Anniversary's multiplayer.