I'm fast af boi, no one can steal my suggestion.

Sale 1: Untrace.

https://backpack.tf/profiles/76561198077729072#!/compare/1552694400/1553558400

https://backpack.tf/profiles/76561198127278508#!/compare/1534896000/1554336000

Sale 2: Untrace.

https://backpack.tf/profiles/76561198203017400#!/compare/1558828800/1559952000

https://backpack.tf/profiles/76561198160120451#!/compare/1558828800/1558915200 - Eldritch Flame Hellmet's history isn't matching.

Sale 3: ~15 Keys.

Sold For Kill-a-Watt Backbiter's Billycock (11.5) + 3 Keys = 14.5 keys.

https://backpack.tf/profiles/76561198160120451#!/compare/1559347200/1559433600

Kill-a-Watt Backbiter's Billycock's Mini:

https://backpack.tf/suggestion/5cfbec47d381721ba11a9623

Sale 4: Untrace.

https://backpack.tf/profiles/76561198203738947#!/compare/1559001600/1559433600

https://backpack.tf/profiles/76561198123224716#!/compare/1559347200/1559433600

Sale 5: Transfer?

https://backpack.tf/profiles/76561198152819850#!/compare/1553558400/1553731200

https://backpack.tf/profiles/76561198043936328#!/compare/1553644800/1553731200

https://marketplace.tf/items/30128;5;u57

Sale 6: Suppppper Lowww.

Mar 28

https://marketplace.tf/items/30128;5;u57

Sale 7: ~21 Keys.

May 22

$37.99 / $1.79 = 21.22 keys

Sales: 15/21

Going with 15-21 keys.

Thanks to scourge for the premium!