Chemically fast.

http://backpack.tf/item/2466362573

Sale 1) Sold + 1 Key for a Max's Head (23 Keys) + Strange Killstreak C.A.P.P.E.R (~7 Keys)

http://backpack.tf/profiles/76561198102805459#!/compare/1473724800/1473811200 - Buyer's Backpack

30 - 1 = 29 Keys

Sale 2) Sold for a Massed Flies Pyro's Beanie (17 Keys) + Orbiting Fire Larrikin Robin (15.5 Keys)

http://backpack.tf/profiles/76561198123087933#!/compare/1474588800/1474675200

17 + 15.5 = 32.5, which rounds to 33 Keys.

Beanie Mini

http://backpack.tf/profiles/76561198176125115#!/compare/1474588800/1474675200 - Sold for a Smoking Conjurer's Cowl (17 Keys)

Larrikin Mini

http://backpack.tf/profiles/76561198128817586#!/compare/1473292800/1473379200 - Sold for a Bubbling Boron Beanie + ~4 Keys of Items

http://www.tf2outpost.com/trade/28476403 - Capped by the Buyout of 15.5 Keys