Sale 1:

Sold for Pro. KS Aus Blutsauger (~6.75) + ~6 keys in metal/items

Seller: https://backpack.tf/profiles/76561198079488962#!/compare/1540684800/1541030400

Buyer: https://backpack.tf/profiles/76561198154040911#!/compare/1540252800/1541635200

https://backpack.tf/item/7050036405

X = 13

Sale 2:

Sold to a bot with a ref for 11 keys

Seller: https://backpack.tf/profiles/76561198055969370#!/compare/1546128000/1546214400

Buyer: https://backpack.tf/profiles/76561198448207173#!/compare/1546128000/1546214400

https://backpack.tf/item/6943129805

X = 11

Sale 3:

Untraceable

Seller: https://backpack.tf/profiles/76561198112387904#!/compare/1536278400/1539216000

Buyer: https://backpack.tf/profiles/76561198202186637#!/compare/1539129600/1539216000

https://backpack.tf/item/7050036405

Only the items added with the hat, and 5 keys + some ref coming from the buyer match.

Sale 4:

Untraceable

Seller: https://backpack.tf/profiles/76561198202186637#!/compare/1539475200/1539561600

Buyer: https://backpack.tf/profiles/76561198079488962#!/compare/1539216000/1540684800

https://backpack.tf/item/7050036405

https://backpack.tf/item/6466794476 - dumped on some bot thing

Sellers:

https://i.imgur.com/ON8m1oH.png

https://backpack.tf/item/6943129805 - ~11.5 keys

Sales at:

11

13

Going with 11-13.