Sale 1 :

Before : http://backpack.tf/profiles/76561198092902341?time=1433228400

After : http://backpack.tf/profiles/76561198092902341?time=1433314800

Sold for an Orbiting Planets Surgeon's Stahlhelm ( 16 keys ) but 2 keys were added : 16 - 2 = 14 keys

Sale 2 : http://www.tf2outpost.com/trade/26270389

Before : http://backpack.tf/profiles/76561198068875113?time=1436598000

After : http://backpack.tf/profiles/76561198068875113?time=1436684400

Sold for 16 keys.

Sale 3 :

Before : http://backpack.tf/profiles/76561198112866447?time=1434956400

After : http://backpack.tf/profiles/76561198112866447?time=1435129200

Sold for a Circling Peace Sign Carouser's Capotain : 13 keys

Mini on the capotain :

Before : http://backpack.tf/profiles/76561198112866447?time=1435302000

After : http://backpack.tf/profiles/76561198112866447?time=1435388400

Sold for a Smoking Big Country : 14 * 0.9 = 13 keys

Taking the range of 13-16 keys.

Supportive criticism welcome