I got a copy of halo reach second hand from an older cousin. On the box it says includes free recon helmet. When I got the game it didn’t have any slips inside it other then the game manual. Is there a way to unlock The Recon Helmet in game?
If it’s the variant I’m thinking of OP, then no there’s no way to get that. You needed a code to unlock it which would have came with the game (generally by pre-ordering). I would guess that your cousin already used the code
The Recon helmet is unlockable at the rank of Colonel for 100,000 Credits, but the variant which the game case tells you of, an attachment called UA/HUL[3], had to be downloaded through Xbox Live via a card with a download code on it. If the card was removed from the case prior to it coming into your possession then you’re unable to get that attachment, but you can still unlock the helmet itself as explained previously.
I bought my copy at a pawn shop last year which included the card, so I was able to download it. If you can get an unused card then they do still work.