Sale 1: 15 Keys Pure. (QS)

https://backpack.tf/profiles/76561198166743890#!/compare/1582761600/1584489600

https://backpack.tf/profiles/76561198308772967#!/compare/1584316800/1584489600

Sale 2: Untrace.

https://backpack.tf/profiles/76561198308772967#!/compare/1585353600/1585526400

https://backpack.tf/profiles/76561198820841831#!/compare/1585440000/1585526400

Sale 3: Untrace.

https://backpack.tf/profiles/76561199015532580#!/compare/1584835200/1584921600

https://backpack.tf/profiles/76561198119624795#!/compare/1583280000/1584921600

Sale 4: Untrace.

https://backpack.tf/profiles/76561198267189538#!/compare/1584662400/1584748800

https://backpack.tf/profiles/76561198142862130#!/compare/1584576000/1585180800

Sale 5: 17 Keys Pure.

https://backpack.tf/profiles/76561198097232731#!/compare/1579219200/1579305600

https://backpack.tf/profiles/76561198445289661#!/compare/1579132800/1579219200

Sale 6: 16 keys pure.

https://backpack.tf/profiles/76561198859721638#!/compare/1584489600/1584576000

https://backpack.tf/profiles/76561198077870175#!/compare/1584403200/1584489600

Sale 7: Untrace.

https://backpack.tf/profiles/76561198077870175#!/compare/1584489600/1584576000

https://backpack.tf/profiles/76561198232949432#!/compare/1583971200/1585872000

Sale 8: 16 Keys pure.

https://backpack.tf/profiles/76561198317418604#!/compare/1584662400/1584835200

https://backpack.tf/profiles/76561198856548187#!/compare/1584748800/1584835200

Sale 9: Untrace.

https://backpack.tf/profiles/76561198856548187#!/compare/1585180800/1585958400

https://backpack.tf/profiles/76561198130650095#!/compare/1585785600/1585872000

Sale 10: 18 Keys pure.

https://backpack.tf/profiles/76561198317418604#!/compare/1580342400/1580774400

https://backpack.tf/profiles/76561198047852423#!/compare/1580688000/1580774400

Sale 11: Use there.

https://backpack.tf/profiles/76561198047852423#!/compare/1581811200/1582070400

https://backpack.tf/profiles/76561198089298088#!/compare/1578182400/1581811200

Sold with some sweets for Verdant Vortex Berlin Brain Bowl.

Sale 12: QS.

https://backpack.tf/profiles/76561198089298088#!/compare/1581811200/1581984000

https://backpack.tf/profiles/76561198087806226#!/compare/1581724800/1581811200

https://marketplace.tf/items/tf2/30810;5;u110

Sale 13: 16 Keys.

Feb 10 $28.9 / $1.78 = 16.24 keys

https://backpack.tf/item/5213497069 - B/O https://bot.tf/stats/listings/M0D6310Z

Sale 14: 19 keys.

Feb 11 $33.95 / $1.77 = 19.18 keys

Couldn't find history.

Sale 15: 16 keys.

Feb 24 $29 / $1.76 = 16.48 keys

https://backpack.tf/item/7171798642

No b/o

Sale 16: 16 keys.

Feb 25 $29 / $1.77 = 16.38 keys

https://backpack.tf/item/7171798642 - No B/O

Sale 17: QS

Feb 29 $24.2 / $1.74 = 13.91 keys

Sale 18: High.

Mar 10 $39.98 / $1.73 = 23.11 keys

https://backpack.tf/item/5205306554 - No B/O

Sale 19: 18 Keys.

Mar 21 $29.99 / $1.68 = 17.85 keys

Couldn't find history.

Sale 20: 21 keys.

Mar 24 $34.99 / $1.68 = 20.83 keys

Couldn't find history.

Sale 21: 21 keys.

Mar 29 $34.99 / $1.69 = 20.70 keys

Couldn't find history.

Sale 22: 20 keys.

Apr 3 $34.64 / $1.70 = 20.38 keys

Couldn't find history.

Sale 23: QS.

$24.24 / $1.72 = 14.09 keys

Couldn't find history.

Sales: 15/16/16/16/16/16/16/17/18/18/19/20/21/21/23

Going with 16-21 keys. - Thanks to shiffle spy

Also thanks to 🔥Master Throne Crimson🔥 for the histories!