Using the standard last 3 months.

Sale 1:

Sold for 14 keys + 14 ref

Seller: https://backpack.tf/profiles/76561198258264645#!/compare/1545868800/1545955200

Buyer: https://backpack.tf/profiles/76561198146265553#!/compare/1545868800/1545955200

https://backpack.tf/item/2699187041

X = 14

Sale 2:

Sold to a bot for 8 keys + ~0.5 keys in metal

Seller: https://backpack.tf/profiles/76561198849539654#!/compare/1551052800/1551225600

Buyer: https://backpack.tf/profiles/76561198305494036#!/compare/1550966400/1551052800

https://backpack.tf/item/4531003320

X = 8.5

Other Sales:

https://backpack.tf/item/6305508185 (#1 & #2)

https://backpack.tf/item/2699187041 (#3 & #4)

#1

Bulk for Purple Confetti Rotation

https://backpack.tf/profiles/76561198200429330#!/compare/1552780800/1552953600

https://backpack.tf/profiles/76561198125791160#!/compare/1552694400/1552780800

#2

Untraceable

https://backpack.tf/profiles/76561198305494036#!/compare/1552953600/1553040000

https://backpack.tf/profiles/76561198163800757#!/compare/1552953600/1553040000

https://i.imgur.com/7y2tPIG.png - Labelled as 12 keys + 25 ref

#3

Bulk for Unusual RL

https://backpack.tf/profiles/76561198146265553#!/compare/1549238400/1549497600

https://backpack.tf/profiles/76561198060828964#!/compare/1549411200/1549497600

#4

A little bulky

https://backpack.tf/profiles/76561198060828964#!/compare/1549497600/1551398400

https://backpack.tf/profiles/76561198055544256#!/compare/1551312000/1551398400

Sellers:

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

https://backpack.tf/item/6305508185 - 15 keys

Sales at:

8.5

14

8.5 went to a quickbuyer, excluding.

Going with 14 flat.