Sale 1:

Sold for 16 keys

Seller: https://backpack.tf/profiles/76561198024867201#!/compare/1552176000/1552262400

Buyer: https://backpack.tf/profiles/76561198079363927#!/compare/1552176000/1552262400

https://backpack.tf/item/5480125226

X = 16

Sale 2:

Sold for 15 keys

Seller: https://backpack.tf/profiles/76561198334598690#!/compare/1548288000/1548374400

Buyer: https://backpack.tf/profiles/76561198132072336#!/compare/1548288000/1548374400

https://backpack.tf/item/4972857104

X = 15

Marketplace Sales:

https://marketplace.tf/items/1168;5;u3015

https://manic.tf/keyprice/?at=2019-01-26 - $33.33 / $1.8 = 18.52 keys

https://manic.tf/keyprice/?at=2019-02-06 - $29 / $1.81 = 16.02 keys

https://manic.tf/keyprice/?at=2019-02-20 - $32.99 / $1.79 = 18.43 keys

https://manic.tf/keyprice/?at=2019-03-13 - $33.33 / $1.79 = 18.62 keys

https://manic.tf/keyprice/?at=2019-03-23 - $17.78 / $1.81 = 9.82 keys

https://manic.tf/keyprice/?at=2019-03-24 - $19.88 / $1.8 = 11.04 keys

https://manic.tf/keyprice/?at=2019-03-26 - $32.50 / $1.77 = 18.36 keys

https://backpack.tf/item/4953079642 - 26th Jan, couldn’t find b/o

https://backpack.tf/item/4988505563 - 20th Feb, couldn’t find b/o

Couldn’t find any other histories with marketplace sales.

X = 19 (2x)

X = 18 (2x)

X = 16

X = 11

X = 10

Other Sales:

https://backpack.tf/item/4953290742 - scrap/gambled

Sellers:

https://i.imgur.com/pLMIV0w.png

https://backpack.tf/item/5034234189 - 19 keys

Sales at:

10

11

15

16 (2x)

18 (2x)

19 (2x)

10 and 11 are outliers. Excluding 10 and 11.

Going with 15-19.