Sellers:

http://imgur.com/a/l4om7 - b/o: 25 keys (13 days, 3 for sale)

Sold:

http://www.tf2outpost.com/trade/29140802

https://backpack.tf/profiles/76561198091539797#!/compare/1494720000/1495065600 - sold for 22 keys

Credits to BLIND

http://www.tf2outpost.com/trade/28887456

https://backpack.tf/profiles/76561198179707937#!/compare/1492819200/1492905600 - sold for Purple Confetti Sergeant's Drill Hat + 2 keys = 27 keys (outlier)

https://backpack.tf/profiles/76561198179707937#!/compare/1491782400/1491868800 - ?

https://backpack.tf/profiles/76561198127938353#!/compare/1491782400/1491868800 - ?

https://backpack.tf/profiles/76561198028125023#!/compare/1490054400/1490140800 - bulk

https://backpack.tf/profiles/76561198080179568#!/compare/1492819200/1492905600

https://backpack.tf/profiles/76561198079240572#!/compare/1492732800/1492992000 - ?

https://backpack.tf/profiles/76561198016157051#!/compare/1491955200/1492041600

https://backpack.tf/profiles/76561198080179568#!/compare/1491868800/1491955200 - scm

https://backpack.tf/profiles/76561198316193894#!/compare/1489363200/1489449600 - ?

https://backpack.tf/profiles/76561198250448148#!/compare/1488931200/1489449600 - sold for 19 keys (low)

https://backpack.tf/profiles/76561198084686265#!/compare/1488931200/1489190400 - ?

http://backpack.tf/profiles/76561197998145090#!/compare/1496275200/1496361600 - sold for Circling Heart Scotch Bonnet (24) = 24 keys

Credits to Mindacos

Conclusion:

sales at 19, 22, 24, 27

seller at 25 (3 in stock)

taking 22-24 keys

Previous Suggestion: http://backpack.tf/suggestion/591de1180e2cad52e87afba8