Link 1: "NoXoN" offers 2 keys and 2 ref on a v. football helmet. No special levels involved.

Link 2: "en_blaze" offers 3 keys each for two hats, which includes the v. football helmet. I was hesitant to put the hat up to a 3-key maximum because I do not feel 3 keys is a typical offer on this hat. If necessary, someone else can do this.

Link 3: "en_blaze" makes a 2-key offer on the hat.

Link 4: Trader offers 2 keys on hat, retracts because they were able to buy one for two keys. Someone else offers 3 ToD tickets (5 ref).

Additional Evidence:

http://www.tf2outpost.com/trade/7866958 - Trader mentions c/o of 2 keys, but does not say where it is from. Also has an offer of a clean FDU and vintage sharpened volcano fragment.

http://www.tf2outpost.com/trade/7838630 - 2 keys + 1.66 ref offer.

http://www.tf2outpost.com/trade/7232507 - 3 keys + 1 ref offer.