Marketplace Sales:

https://marketplace.tf/items/tf2/31157;5;u3115

https://backpack.tf/item/10521165945 - Very likely August 19th, compare links would suggest

https://backpack.tf/item/12777136575 - August 29th

$8.99, June 18th, August 19th & 29th

https://marketplace.tf/items/tf2/5021;6 - keys were:

$1.99, June 18th

$1.83, August 19th

$1.81, August 29th

8.99/1.99 = 4.518, rounds to 4.5 keys

8.99/1.83 = 4.913, rounds to 4.9 keys

8.99/1.81 = 4.967, rounds to 4.95 keys

Other Sales:

#1

https://backpack.tf/profiles/76561199026390261#!/compare/1752710400/1752796800

https://backpack.tf/profiles/76561199198723851#!/compare/1752192000/1753315200

https://backpack.tf/item/12432839214

Untraceable

#2

https://backpack.tf/profiles/76561199522047597#!/compare/1755043200/1755648000

https://backpack.tf/profiles/76561197963500354#!/compare/1755129600/1755734400

https://backpack.tf/item/13323398177

Untraceable, most likely SCM

Sellers:

https://marketplace.tf/items/tf2/31157;5;u3115

https://backpack.tf/item/13323398177 - $8.99 (~5 keys)

https://backpack.tf/item/12902577670 - $8.99

Sales at:

4.5

4.9

4.95

Taking 4.5-4.95 keys.