Sale 1:

Sold for 3 keys + 12.11 ref

Seller: https://backpack.tf/profiles/76561198206121028#!/compare/1543536000/1543795200

Buyer: https://backpack.tf/profiles/76561198044335614#!/compare/1543449600/1543536000

https://backpack.tf/item/6649313823

X = 3.5

Sale 2:

Sold for 3 keys + 12 ref

Seller: https://backpack.tf/profiles/76561198242646048#!/compare/1543795200/1543881600

Buyer: https://backpack.tf/profiles/76561198334598690#!/compare/1543795200/1543881600

https://backpack.tf/item/6367161996

https://i.imgur.com/0CqQDtj.png - bot.tf confirms

X = 3.5

Marketplace Sales:

https://marketplace.tf/items/30614;5;u3010

24/11 - $7.59 (5x), https://manic.tf/keyprice/?at=2018-11-24 - $7.59 / $1.73 = 4.39 keys

25/11 - $5, https://manic.tf/keyprice/?at=2018-11-25 - $5 / $1.73 = 2.89 keys

30/11 - $5.16, https://manic.tf/keyprice/?at=2018-11-30 - $5.16 / $1.72 = 3.00 keys

6/12 - $7.79, https://manic.tf/keyprice/?at=2018-12-06 - $7.79 / $1.7 = 4.58 keys

9/12 - $5.22, https://manic.tf/keyprice/?at=2018-12-09 - $5.22 / $1.68 = 3.11 keys

12/12 - $5.22, https://manic.tf/keyprice/?at=2018-12-12 - $5.22 / $1.65 = 3.16 keys

X = 4.5 (6x)

X = 3 (4x)

Other Sales:

https://backpack.tf/item/7047974047 (#1)

https://backpack.tf/item/6353118492 (#2)

https://backpack.tf/item/4444264480 (#3)

https://backpack.tf/item/3844101125 (#4)

https://backpack.tf/item/6367161996 (#5)

https://backpack.tf/item/4396979178 - Gambled/marketplace

https://backpack.tf/item/7046152581 - Gambled/marketplace

https://backpack.tf/item/5406743549 - gambled

https://backpack.tf/item/4452170779 - marketplace

https://backpack.tf/item/6474686386 - scammer

https://backpack.tf/item/3872135482 - scammer

https://backpack.tf/item/4863977006 - scammers

https://backpack.tf/item/3892303763 - scrap

https://backpack.tf/item/4537085242 - mannco

#1

Untraceable

https://backpack.tf/profiles/76561198335791307#!/compare/1543795200/1543881600

https://backpack.tf/profiles/76561198142650557#!/compare/1543363200/1543881600

https://i.imgur.com/0CqQDtj.png - labelled as 4 keys

#2

Untraceable

https://backpack.tf/profiles/76561198034869174#!/compare/1543536000/1543622400

https://backpack.tf/profiles/76561198155110999#!/compare/1543449600/1543536000

#3

Untraceable

https://backpack.tf/profiles/76561198313915836#!/compare/1544745600/1544832000

https://backpack.tf/profiles/76561198363395191#!/compare/1544745600/1544832000

#4

Untraceable

https://backpack.tf/profiles/76561198096649811#!/compare/1543536000/1543708800

https://backpack.tf/profiles/76561198870135047#!/compare/1543622400/1543708800

#5

Untraceable

https://backpack.tf/profiles/76561198334598690#!/compare/1543968000/1544140800

https://backpack.tf/profiles/76561198296439158#!/compare/1544054400/1544227200

https://i.imgur.com/0CqQDtj.png - labelled as 4 keys on bot.tf

2nd link most likely isn’t the buyer

Sellers:

https://i.imgur.com/4KjFvvp.png

https://backpack.tf/item/6649313823 - ~3.9 keys

https://backpack.tf/item/6299214047 - ~3.9 keys

https://backpack.tf/item/3844101125 - ~3.9 keys

Sales at:

3 (4x)

3.5 (2x)

4.5 (6x)

The sales at 3 and 4.5 are all marketplace sales, and are all either too high or too low due to sellers. Excluding 3 and 4.5.

Going with 3.5 flat.