Re-suggesting.

Using sales from the last suggestion onwards.

Sale 1:

Sold for 11 keys

Seller: https://backpack.tf/profiles/76561198024867201#!/compare/1534723200/1534809600

Buyer: https://backpack.tf/profiles/76561198356805608#!/compare/1533772800/1534896000

https://backpack.tf/item/4249872478

X = 11

Sale 2:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198334598690#!/compare/1536451200/1536537600

Buyer: https://backpack.tf/profiles/76561198262802628#!/compare/1535846400/1536537600

https://backpack.tf/item/4204320225

X = 10

Sale 3:

Sold for 7 keys + ~2 keys in metal/items

Seller: https://backpack.tf/profiles/76561198063640894#!/compare/1536451200/1536537600

Buyer: https://backpack.tf/profiles/76561198026605090#!/compare/1536537600/1536710400

https://backpack.tf/item/4398207617

X = 9

Sale 4: - Credit to K1ng

Seller: https://backpack.tf/profiles/76561198363395191#!/compare/1537488000/1537574400

Buyer: https://backpack.tf/profiles/76561198309100349#!/compare/1537488000/1537574400

https://backpack.tf/item/6557345963

X = 8

Sale 5:

Sold for 7 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198254667858#!/compare/1535414400/1535500800

Buyer: https://backpack.tf/profiles/76561198363395191#!/compare/1535414400/1535500800

https://backpack.tf/item/5487141390

X = 7.5

Other Sales:

https://backpack.tf/item/6614112981 (#1)

https://backpack.tf/item/6557345963 (#2 & #3)

https://backpack.tf/item/5487141390 (#4)

https://backpack.tf/item/5386898321 (#5)

https://backpack.tf/item/4204320225 (#6)

https://backpack.tf/item/6272443114 - bot stuff

#1

Untraceable

https://backpack.tf/profiles/76561198353678309#!/compare/1536278400/1536710400

https://backpack.tf/profiles/76561198348126416#!/compare/1536278400/1536796800

#2

Bulk for pure

https://backpack.tf/profiles/76561198311498888#!/compare/1534896000/1534982400

https://backpack.tf/profiles/76561198154477915#!/compare/1534723200/1534982400

#3

Untraceable

https://backpack.tf/profiles/76561198154477915#!/compare/1534982400/1536105600

https://backpack.tf/profiles/76561198363395191#!/compare/1536019200/1536105600

#4

Untraceable

https://backpack.tf/profiles/76561198363395191#!/compare/1537056000/1537142400

https://backpack.tf/profiles/76561198282372085#!/compare/1537056000/1537142400

#5

Untraceable, most likely scm

https://backpack.tf/profiles/76561198192632255#!/compare/1534982400/1535155200

https://backpack.tf/profiles/76561198070141659#!/compare/1536364800/1537056000

#6

Untraceable

https://backpack.tf/profiles/76561198204995668#!/compare/1535932800/1536019200

https://backpack.tf/profiles/76561198334598690#!/compare/1535932800/1536019200

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

Sellers:

https://i.imgur.com/LU6eFQS.png

https://i.imgur.com/kwzNn9X.png

https://backpack.tf/item/6557345963 - 10 keys

https://backpack.tf/item/4313377206 - 18 keys

https://backpack.tf/item/5171481787 - 20 keys

https://backpack.tf/item/4448708976 - 20 keys

https://backpack.tf/item/4364777185 - 30 keys

Sales at:

7.5

8

9

10

11

Going with 8-11, as requested by K1ng.