Credit to K1ng for the help!

Sale 1)

Seller: https://next.backpack.tf/profiles/76561198156749406/compare?from=1721952000&to=1722124800

Buyer: https://next.backpack.tf/profiles/76561199079803267/compare?from=1722038400&to=1722124800

Item History: https://next.backpack.tf/item/14722385482

20 Keys

Sale 2)

Seller: https://backpack.tf/profiles/76561198064724507#!/compare/1724803200/1724889600

Buyer: https://backpack.tf/profiles/76561198047595874#!/compare/1724803200/1724889600

Item History: https://next.backpack.tf/item/14739780902

Sold with an Australium Eyelander, 1 Key, Elemental Laugh Taunt, Spectral Shackles Rancho Relaxo, Carioca's Call Square Dance Taunt, Desert Wind Conga, Desert Wind Kazotzky Kick, Amatory Didgeridrongo, Electrocution Rocket Jockey, and Distress Signal Bare Knuckle Beatdown for a Strange Circling TF Logo Prehistoric Pullover.

Sale 3)

https://backpack.tf/profiles/76561199079803267#!/compare/1725148800/1725580800

https://backpack.tf/profiles/76561199111073161#!/compare/1725494400/1725580800

https://backpack.tf/item/14435462917

Untraced

Sale 4)

https://marketplace.tf/items/tf2/31271;5;u19

https://backpack.tf/item/12116642342

Sold for $41.99 on July 27

https://marketplace.tf/items/tf2/5021;6

Keys were at $1.72

41.99/1.72 = ~ 24 keys

Sale 5)

https://marketplace.tf/items/tf2/31271;5;u19

https://backpack.tf/item/12849063254

Sold for $41.99 on September 14

https://marketplace.tf/items/tf2/5021;6

Keys were at $1.88

41.99/1.88= ~ 22 keys

Sale 6)

https://backpack.tf/item/12639053883

Excluding all bot dumps and bot transfers

https://backpack.tf/profiles/76561198062747535#!/compare/1726099200/1726185600

https://backpack.tf/profiles/76561199125443371#!/compare/1726099200/1726185600

Untraced

I can revise this range to 20 - 24 keys or an average of 22 Keys Flat.