Sale 1:

Sold with half a key in ref for Dead Presidents L’Inspecteur (Suggestion at 13) + 2 keys

Seller: https://backpack.tf/profiles/76561198348057478#!/compare/1551830400/1551916800

Buyer: https://backpack.tf/profiles/76561198076610032#!/compare/1551830400/1551916800

https://backpack.tf/item/7397249256

X = 15

Sale 2:

Sold for 14 keys

Seller: https://backpack.tf/profiles/76561198341171690#!/compare/1548201600/1548288000

Buyer: https://backpack.tf/profiles/76561198084182003#!/compare/1548288000/1548720000

https://backpack.tf/item/7397249256

Buyer sold the KE to a quickbuyer, then used the keys on the hat on the same day.

X = 14

Other Sales:

https://backpack.tf/item/7397249256 (#1 & #2)

https://backpack.tf/item/6771825258 - scrap

#1

Untraceable

https://backpack.tf/profiles/76561198314264870#!/compare/1545609600/1545955200

https://backpack.tf/profiles/76561198341171690#!/compare/1545868800/1545955200

#2

Untraceable

https://backpack.tf/profiles/76561198239242582#!/compare/1550620800/1550707200

https://backpack.tf/profiles/76561198348057478#!/compare/1550620800/1550707200

Dead Presidents L’inspecteur:

https://backpack.tf/suggestion/5c89c9756780720bb20378cd

Sellers:

https://i.imgur.com/1oZy9s8.png

https://backpack.tf/item/6771825258 - 15 keys

Sales at:

14

15

Going with 14-15.