Found some usable & trackable sales for you.

1)

http://backpack.tf/profiles/76561198160716039#!/compare/1470355200/1470441600

Sold for 11 pure keys + ~1 key in sweets.

X = 12 keys

2)

http://backpack.tf/profiles/76561198119082031#!/compare/1470441600/1470528000

Sold for 10 pure keys + ~2 keys in sweets.

X = 12 keys.

3)

http://backpack.tf/profiles/76561198260796217#!/compare/1470614400/1470700800

http://backpack.tf/profiles/76561198119082031#!/compare/1470528000/1470700800

Sold for Orbiting Fire Rimmed Raincatcher + Taunt: Mannrobics.

http://www.tf2outpost.com/trade/28398150 BO 13 keys 9 refined

Rounding to 13 keys flat.

4)

http://backpack.tf/profiles/76561198071713766#!/compare/1471305600/1471478400

Sold with ~7 keys of items for Smoking Noble Amassment of Hats.

Will be used to update the Noble.

5)

http://backpack.tf/profiles/76561198163724445#!/compare/1471132800/1471305600

http://backpack.tf/profiles/76561198071713766#!/compare/1471219200/1471305600

Sold for a duped Kill-a-Watt Birdcage + ~1 key in items.

X = 12 keys.

Mini on duped Kill-a-Watt Birdcage:

http://backpack.tf/profiles/76561198070558874#!/compare/1469923200/1470009600

Sold for 11 pure keys.

Summary: 12-13 keys.