Sale 1: ~24 Keys Pure.

https://backpack.tf/profiles/76561198231082180#!/compare/1553558400/1553644800

https://backpack.tf/profiles/76561198254541735#!/compare/1552867200/1554508800

Sale 2: Use there.

Sold For Terror-Watt Field Practice.

https://backpack.tf/profiles/76561198254541735#!/compare/1554508800/1554854400

https://backpack.tf/profiles/76561198062476297#!/compare/1554422400/1554681600

Sale 3: Untrace/Bulk.

https://backpack.tf/profiles/76561198048591417#!/compare/1553817600/1553904000

https://backpack.tf/profiles/76561198048851745#!/compare/1553817600/1553904000

Sale 4: QS.

https://backpack.tf/profiles/76561198048851745#!/compare/1554249600/1554336000 - Only 19 keys matched.

https://backpack.tf/profiles/76561198830746068#!/compare/1554249600/1554336000

Sale 5: Untrace/QS.

https://backpack.tf/profiles/76561198309859893#!/compare/1552608000/1553126400

https://backpack.tf/profiles/76561198830746068#!/compare/1552608000/1552694400

Sale 6: Untrace. (SCM, 2 sold that day)

https://backpack.tf/profiles/76561198197898870#!/compare/1556323200/1557187200

https://backpack.tf/profiles/76561198112281935#!/compare/1556582400/1556755200

Marketplace.tf Sales:

https://marketplace.tf/items/30862;5;u8

Sale 7: ~25 Keys.

May 20

$45.00 / $1.83 = 24.59 keys

Sale 8: ~27 Keys.

May 28

$49.50 / $1.81 = 27.35 keys

Usable Sales: 24/25/27

Going with 24-27 keys.

Thanks to scourge for the premium!