Blizzardy Storm Soldered Sensei

Easy.

Selling:

http://imgur.com/a/PirtP

2 young sellers @ ~24

9 days unsold @ 26

Young sellers @ more

Sale 1:

https://marketplace.tf/items/30004;5;u30

Sold for 57.99 USD

58 / 2.1 = 27.62 keys

X = 28 Keys

Sale 2:

http://backpack.tf/profiles/76561198112279227#!/compare/1489276800/1489363200

Added 14 keys for a Stare From Beyond Scotch (41, indate)

41 - 14 = 27

X = 27

Sale 3:

http://backpack.tf/profiles/76561198112279227#!/compare/1492905600/1492992000

Sold for an Insomnia Carachadon (14, indate) + TF Logo Sola (13, indate)

14 + 13 = 27

X = 27

Including 26 in the range due to the 9 day unsold.

26 - 28 keys