Sellers:

http://www.tf2outpost.com/trade/29191377 - b/o: 15 keys (12 days)

http://www.tf2outpost.com/trade/29192658 - b/o: 16 keys (8 days)

http://www.tf2outpost.com/trade/29194317 - b/o: 14 keys (11 days)

Sold:

http://backpack.tf/profiles/76561198060850739#!/compare/1495324800/1496275200

http://backpack.tf/profiles/76561198045368765#!/compare/1495065600/1495411200 - ?

http://www.tf2outpost.com/trade/29181705

http://backpack.tf/profiles/76561198203349487#!/compare/1494892800/1495152000

http://backpack.tf/profiles/76561198060850739#!/compare/1495065600/1495152000 - sold for 10 keys (low)

http://backpack.tf/profiles/76561198046534599#!/compare/1493424000/1493596800 - ?

http://www.tf2outpost.com/trade/28899603

http://backpack.tf/profiles/76561198044668296#!/compare/1493596800/1493856000 - sold for Steaming Front Runner (16) + 2 keys = 15 keys b/o

http://backpack.tf/profiles/76561198344491537#!/compare/1493251200/1493337600 - sold for 13 keys + metal (13)

http://backpack.tf/profiles/76561198107934426#!/compare/1490745600/1490832000 - sold for Strange Specialized Killstreak Australium Grenade Launcher (14) = 14 keys

http://backpack.tf/profiles/76561198087518506#!/compare/1494806400/1494892800 - sold for Smoking Defiant Spartan (13) = 13 keys

Conclusion:

sales at 10, 13, 13, 14, 15

taking 13-15 keys