I have not gotten the classic helmet req pack from E3
You can find all the details about the MixPot reward in this thread:
https://www.halowaypoint.com/en-us/forums/6e35355aecdf4fd0acdaee3cc4156fd4/topics/watch-the-xbox-e3-stream-for-classic-helmet-pack/b3bcc500-a991-41cf-90ff-bae8370ade80/posts