Sale 1:

Sold for 12 keys

Seller: https://backpack.tf/profiles/76561198074621436#!/compare/1547596800/1547683200

Buyer: https://backpack.tf/profiles/76561198194248589#!/compare/1547510400/1547769600

https://backpack.tf/item/7454641746

X = 12

Sale 2:

Sold for Blizzardy Head Hedge (12)

Seller: https://backpack.tf/profiles/76561198006544512#!/compare/1550707200/1550793600

Buyer: https://backpack.tf/profiles/76561198208557484#!/compare/1550275200/1551225600

https://backpack.tf/item/7454641746

X = 12

Sale 3:

Sold for 11 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198315588518#!/compare/1548720000/1548806400

Buyer: https://backpack.tf/profiles/76561198313874926#!/compare/1548806400/1549843200

https://backpack.tf/item/7443961482

https://i.imgur.com/gqaB5v8.png - bot.tf confirms

X = 11

Sale 4:

Sold for 11 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198315588518#!/compare/1548115200/1548201600

Buyer: https://backpack.tf/profiles/76561198153276416#!/compare/1548028800/1548201600

https://backpack.tf/item/7443961482

https://i.imgur.com/gqaB5v8.png - bot.tf confirms

X = 11

Sale 5:

Sold for Slumber Bandito

Seller: https://backpack.tf/profiles/76561198315588518#!/compare/1549152000/1549238400

Buyer: https://backpack.tf/profiles/76561198442272468#!/compare/1549152000/1549238400

https://backpack.tf/item/6956855475

https://i.imgur.com/gqaB5v8.png - B/O of ~11

https://i.imgur.com/wDfjVlG.png - Buyers at 11+ on the Bandito. This easily caps.

X = 11 (Capped by B/O)

Sale 6:

Sold for 11 keys + cheap cosmetic

Seller: https://backpack.tf/profiles/76561198384161769#!/compare/1550880000/1550966400

Buyer: https://backpack.tf/profiles/76561198005147198#!/compare/1550880000/1551225600

https://backpack.tf/item/6956855475

X = 11

Sale 7:

Sold for 10 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198153276416#!/compare/1548720000/1548806400

Buyer: https://backpack.tf/profiles/76561198315588518#!/compare/1548720000/1548806400

https://backpack.tf/item/7443961482

https://i.imgur.com/gqaB5v8.png - bot.tf confirms

X = 10

Sale 8:

Sold for 10 keys + some ref

Seller: https://backpack.tf/profiles/76561198194248589#!/compare/1548892800/1548979200

Buyer: https://backpack.tf/profiles/76561198006544512#!/compare/1548892800/1548979200

https://backpack.tf/item/7454641746

X = 10

Sale 9:

Sold for 10 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198225715416#!/compare/1547856000/1548028800

Buyer: https://backpack.tf/profiles/76561198315588518#!/compare/1547942400/1548028800

https://backpack.tf/item/7443961482

https://i.imgur.com/gqaB5v8.png - bot.tf confirms

X = 10

Sale 10:

Sold for Aces Tricorne (10) + cheap cosmetic

Seller: https://backpack.tf/profiles/76561198076383712#!/compare/1549670400/1549756800

Buyer: https://backpack.tf/profiles/76561198046772407#!/compare/1548979200/1549670400

https://backpack.tf/item/6956855475

X = 10

Sale 11:

Sold for 9 keys + 1.11 ref

Seller: https://backpack.tf/profiles/76561198092435879#!/compare/1538956800/1546992000

Buyer: https://backpack.tf/profiles/76561198308772967#!/compare/1546905600/1546992000

https://backpack.tf/item/6796797915

https://i.imgur.com/gqaB5v8.png - bot.tf confirms

X = 9

Other Sales:

https://backpack.tf/item/7425736937 (#1)

https://backpack.tf/item/7075063275 (#2 & #3)

https://backpack.tf/item/6956855475 (#4-8)

https://backpack.tf/item/6863486218 (#9 & #10)

https://backpack.tf/item/6799410639 - scammer

#1

SCM

https://backpack.tf/profiles/76561198261081239#!/compare/1549497600/1549584000

https://backpack.tf/profiles/76561198048383379#!/compare/1545523200/1550102400

#2

SCM

https://backpack.tf/profiles/76561198138322150#!/compare/1546214400/1546387200

https://backpack.tf/profiles/76561198045775820#!/compare/1546300800/1546387200

#3

SCM

https://backpack.tf/profiles/76561198045775820#!/compare/1546300800/1546387200

https://backpack.tf/profiles/76561198101487802#!/compare/1545004800/1546732800

#4

Untraceable

https://backpack.tf/profiles/76561198442272468#!/compare/1549238400/1549324800

https://backpack.tf/profiles/76561198006544512#!/compare/1549152000/1549238400

#5

Untraceable

https://backpack.tf/profiles/76561198006544512#!/compare/1549497600/1549584000

https://backpack.tf/profiles/76561198076383712#!/compare/1549584000/1549670400

#6

Sold with items for Purple Confetti Backbiter’s Billycock

https://backpack.tf/profiles/76561198046772407#!/compare/1548979200/1549670400

https://backpack.tf/profiles/76561198053717045#!/compare/1549670400/1549756800

Using on the billycock.

#7

Bulk

https://backpack.tf/profiles/76561198053717045#!/compare/1550448000/1550534400

https://backpack.tf/profiles/76561198089298088#!/compare/1550448000/1550534400

#8

Untraceable

https://backpack.tf/profiles/76561198089298088#!/compare/1550880000/1550966400

https://backpack.tf/profiles/76561198384161769#!/compare/1550880000/1550966400

#9

Untraceable

https://backpack.tf/profiles/76561198297466333#!/compare/1548892800/1549584000

https://backpack.tf/profiles/76561198085685517#!/compare/1549497600/1549584000

#10

Untraceable

https://backpack.tf/profiles/76561198308772967#!/compare/1547164800/1547251200

https://backpack.tf/profiles/76561198252734974#!/compare/1546819200/1547424000

Sellers:

https://i.imgur.com/yMXJxiM.png

https://backpack.tf/item/6956855475 - ~11.3 keys

https://backpack.tf/item/6917341709 - 12 keys

https://backpack.tf/item/6784575924 - 13 keys

https://backpack.tf/item/6799410639 - 13 keys

Sales at:

9

10 (4x)

11 (4x)

12 (2x)

9 is countered by buyers at 10. Excluding 9.

Sales at 10 are far too common to be excluded. Keeping 10.

Going with 10-12.