Mario Kart

http://backpack.tf/item/2183686758

Sale 1) Sold for 9 Keys

http://backpack.tf/profiles/76561198056657724#!/compare/1494288000/1494460800

Sale 2) Sold for 11 Keys

http://backpack.tf/profiles/76561198138945248#!/compare/1494979200/1495065600 - Buyer's Backpack

Sale 3) Sold for a Bubbling Stout Shako + 1 Key

http://backpack.tf/profiles/76561198152580447#!/compare/1495238400/1495324800

No sales that I could figure out for the Shako.

http://backpack.tf/item/2248902227

Sale 4) Sold + 1 Key for a Blizzardy Storm Heavy Duty Rag (12 Keys)

http://backpack.tf/profiles/76561198140570855#!/compare/1495411200/1495497600 - Seller's Backpack

http://backpack.tf/profiles/76561198062229215#!/compare/1495324800/1495411200 - Buyer's Backpack

12 - 1 = 11 Keys

Since Sale 2 sold in ~1 Day, I'll call 9 low and go for a passive drop with 11 flat.