Removing 11 per Foamy's advice.

Duck Feet

http://backpack.tf/item/3545522413

Sale 1) Sold for a Strange Burstchester (6.6 Keys) + Strange Spec KS Festive Knife (~6.1 Keys) + Zoomin' Broom (1.7 Keys)

http://backpack.tf/profiles/76561198078674658#!/compare/1487289600/1487376000

6.6 + 6.1 + 1.7 = 14.4, which rounds to 14 Keys

Sale 2) Sold for 12 Keys + ~3 Keys of Items

http://backpack.tf/profiles/76561198066434918#!/compare/1487721600/1487808000

12 + 3 = 15 Keys

Sale 3) Sold + 4 Keys for a Duped Kill-a-Watt Ye Olde Baker Boy (21 Keys)

http://backpack.tf/profiles/76561198010273413#!/compare/1487808000/1487894400

21 - 4 = 17 Keys

Baker Mini

http://backpack.tf/profiles/76561198057671085#!/compare/1491436800/1491523200 - Sold for 15 Keys + ~5 Keys of Items + ~1 Key of Refined

http://backpack.tf/profiles/76561198014811898#!/compare/1486252800/1486771200 - Sold for 20 Keys + ~1 Key of Refined

Sale 4) Sold for a Purple Confetti Helmet Without a Home (13 Keys) + ~3 Keys of Items

http://backpack.tf/profiles/76561198253348344#!/compare/1487980800/1488067200

13 + 3 = 16 Keys

Sale 5) Sold for a Miami Nights Mann of Reason

http://backpack.tf/profiles/76561198093515852#!/compare/1488240000/1488499200

This would better be used for the Mann of Reason, seeing as it's 2 years Outdated.

Sale 6) Sold for a Stormy Storm Coupe D'isaster + ~5 Keys of Items

http://backpack.tf/profiles/76561197961172123#!/compare/1488585600/1488672000

Fits in the range.

Sale 7) Sold for 13 Keys + ~1 Key of Items

http://backpack.tf/profiles/76561197993258470#!/compare/1489017600/1489190400

13 + 1 = 14 Keys