Sale 1: Untrace.

https://backpack.tf/profiles/76561198054534866#!/compare/1556236800/1556496000

https://backpack.tf/profiles/76561198046154815#!/compare/1556409600/1556582400

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Marketplace.tf Sales:

https://marketplace.tf/items/30969;5;u8;strange

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Sale 2: ~31 Keys.

Apr 19

$55.00 / $1.78 = 30.90 keys

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Sale 3: ~22 Keys.

Apr 30

$40.00 / $1.81 = 22.10 keys

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Usable Sales: 22/31

Going with 22-31 keys.

Thanks to scourge for the premium!