The Sale:

Sold for 11 keys

Seller: https://backpack.tf/profiles/76561198023542389#!/compare/1552262400/1552435200

Buyer: https://backpack.tf/profiles/76561198020834409#!/compare/1551830400/1552608000

https://backpack.tf/item/246496534

X = 11

Marketplace Sales:

https://marketplace.tf/items/104;5;u7

https://manic.tf/keyprice/?at=2019-01-21 - $26.7 / $1.75 = 15.26 keys

X = 15

Other Sales:

https://backpack.tf/item/240675917 (#1 & #3, excluded some gambling)

#1

Gambled

https://backpack.tf/profiles/76561198173381547#!/compare/1548633600/1548720000

https://backpack.tf/profiles/76561198875470056#!/compare/1548547200/1548720000

#2

Bulk for Ring of Fire Woolen Warmer

https://backpack.tf/profiles/76561198130834456#!/compare/1551830400/1551916800

https://backpack.tf/profiles/76561198120585187#!/compare/1551830400/1551916800

#3

Untraceable

https://backpack.tf/profiles/76561198120585187#!/compare/1552435200/1552521600

https://backpack.tf/profiles/76561198119149660#!/compare/1552435200/1552521600

Sales at:

11

15

Little iffy on using the marketplace sale, especially given how long the seller of the sale at 11 had it for, though I couldn’t find anything that shows it was listed for that long, so I’ll wave it off this time.

Going with 11-15.