Sale 1:

https://backpack.tf/profiles/76561198288147124#!/compare/1626912000/1630713600

https://backpack.tf/profiles/76561198453530349#!/compare/1626912000/1626998400

Untrace.

Sale 2:

https://backpack.tf/profiles/76561198453530349#!/compare/1633737600/1633824000

https://backpack.tf/profiles/76561198204715857#!/compare/1633651200/1633824000

Untrace.

Sale 3:

https://marketplace.tf/items/tf2/30187;5;u30 - Aug 28

$39.99 / $1.81 = 22.09 keys

= 22 Keys.

Xergoyf: https://backpack.tf/suggestion/61641523f934542f2f6ecde4#comment-61b54af97265a46eb63778b2

OF Tyro + Pink Physician's Procedure Mask

https://backpack.tf/profiles/76561198850274253#!/compare/1625961600/1626048000

https://backpack.tf/profiles/76561198288147124#!/compare/1625961600/1626048000

https://gladiator.tf/listings/60eaf5a3a24b2df4d5ceec65 - b/o was 18, dumped to Scrappy soon after

https://gladiator.tf/listings/60f896225373a3cd317eede9 - caps with buy orders on the Tyro at the time.

https://gladiator.tf/listings/61629fd675170f75483f41ea - Untrace 2 was likely 22

https://backpack.tf/profiles/76561198134910571#!/compare/1626998400/1627603200

17 keys

https://backpack.tf/profiles/76561198348757255#!/compare/1630281600/1630713600

Sold to a bot for 17

https://gladiator.tf/listings/6140baa98cc9edcfd4c2e5b9

https://backpack.tf/profiles/76561198841279602#!/compare/1631491200/1631577600

https://backpack.tf/item/9027065541

Likely sold for 22

$39.99 / $1.87 = 21.39 keys - new mp sale

With the seller at 21 for close to a month + the amount of dumps, this will need a range. 17 - 22 can work, or 18 - 21 to narrow the range slightly.