This hat isn't so bad.

Sold for a Kill-a-Watt Flipped Trilby(12 Keys with Overpay)

http://backpack.tf/profiles/76561198043776684?time=1422540412 -> http://backpack.tf/profiles/76561198043776684?time=1422604800

Sold for a Bubbling Charmer's Chapeau(11 Keys with Overpay)

http://backpack.tf/profiles/76561198127214200?time=1425456000 -> http://backpack.tf/profiles/76561198127214200?time=1425542400

Sold for a Blizzardy Storm Ye Olde Baker Boy(12 Keys with Overpay)

http://www.tf2outpost.com/item/440,3439727210,721,5 Conquistador History

http://www.tf2outpost.com/item/440,3440133495,107,5 Baker History

Sold for a Nuts & Bolts Lucky Shot(11 Keys with Overpay)

http://backpack.tf/profiles/76561198065480853?time=1423521410 -> http://backpack.tf/profiles/76561198065480853?time=1423555200

Sales seem to fit, 11-12 Keys should be fine.

Additional Proof/Counter-Proof/Constructive Criticism/Feedback is always appreciated.