Sellers: https://gyazo.com/20a35619d7a4a272303ab2be91a9f7eb

https://backpack.tf/item/3842992198 - 1 day @ 29 keys

https://backpack.tf/item/3557439140 - 2 days @ 30

Sales:

Sale 1: 31

https://backpack.tf/profiles/76561198128506921#!/compare/1534636800/1539561600

https://backpack.tf/profiles/76561198236099496#!/compare/1535328000/1535673600

Sale 2: Untraceable

https://backpack.tf/profiles/76561198236099496#!/compare/1536710400/1536796800

https://backpack.tf/profiles/76561198261486591#!/compare/1536710400/1539561600

Sale 3: Bulk

https://backpack.tf/profiles/76561198261486591#!/compare/1536710400/1539561600

https://backpack.tf/profiles/76561198297526222#!/compare/1536710400/1536796800

Sale 4: Untraceable

https://backpack.tf/profiles/76561198297526222#!/compare/1536796800/1536883200

https://backpack.tf/profiles/76561198113167601#!/compare/1536796800/1536883200

Sale 5: Untraceable

https://backpack.tf/profiles/76561198113167601#!/compare/1537142400/1537228800

https://backpack.tf/profiles/76561198075108450#!/compare/1537142400/1537228800

Sale 6: 25.1

https://backpack.tf/profiles/76561198075108450#!/compare/1537574400/1537660800

https://backpack.tf/profiles/76561198280357510#!/compare/1537574400/1537660800

Sale 7: 24.2

https://backpack.tf/profiles/76561198280357510#!/compare/1537660800/1539475200

https://backpack.tf/profiles/76561198141410640#!/compare/1539216000/1539388800

Sale 8: Untraceable

https://backpack.tf/profiles/76561198004311443#!/compare/1538265600/1538524800

https://backpack.tf/profiles/76561198363395191#!/compare/1538438400/1538524800

Sale 9: Untraceable

https://backpack.tf/profiles/76561198072140772#!/compare/1538438400/1538611200

Sale 10: Untraceable

https://backpack.tf/profiles/76561198072140772#!/compare/1538784000/1538870400

https://backpack.tf/profiles/76561198079828696#!/compare/1538784000/1538870400

Sale 11: 23.4

https://backpack.tf/profiles/76561198266876790#!/compare/1539043200/1539129600

https://gyazo.com/c975bf5edf456464872ad46698dc35cc

Sale 12: 25

https://backpack.tf/profiles/76561198266876790#!/compare/1539388800/1539475200

https://backpack.tf/profiles/76561198266876790#!/compare/1539388800/1539475200

Sold for 24 pure + Kazotsky Kick (1)

Sale 13: 16

https://backpack.tf/profiles/76561198132111326#!/compare/1539388800/1539475200

Sold for Smoking Human Cannonball (16)

So we've got 16, 23.4, 24.2, 25, 25.1, 31. Excluding 16 as its an obvious exception. Going with 23-31