Item 1

https://backpack.tf/item/4261719448

Sale 1

https://backpack.tf/profiles/76561199059160806#!/compare/1684022400/1684195200

https://backpack.tf/profiles/76561198205194977#!/compare/1684022400/1684195200

28 keys

Item 2

https://backpack.tf/item/12180200201

Sale 2

https://backpack.tf/profiles/76561198060734100#!/compare/1690070400/1690502400

https://backpack.tf/profiles/76561198339104273#!/compare/1690070400/1690329600

18 keys?

Item 3

https://backpack.tf/item/7939709092

Can't use this

Item 4

https://backpack.tf/item/6424448225

Sale 3

https://backpack.tf/profiles/76561199026390261#!/compare/1683504000/1683590400

https://backpack.tf/profiles/76561198096144879#!/compare/1683417600/1683504000

https://imgur.com/a/uqeqUGa

Sell order might have changed, but I can match 25 keys

Item 5

https://backpack.tf/item/5214535955

Sale 4

https://backpack.tf/profiles/76561197998850076#!/compare/1689120000/1689811200

https://backpack.tf/profiles/76561198157964204#!/compare/1689033600/1689724800

No clue

Sale 5

https://backpack.tf/profiles/76561198157964204#!/compare/1689724800/1689811200

https://backpack.tf/profiles/76561198093692174#!/compare/1688947200/1689897600

Bulk for a Misty Skull Sergeant's Drill Hat

Sale 6

https://backpack.tf/profiles/76561198093692174#!/compare/1689897600/1690243200

https://backpack.tf/profiles/76561198830682097#!/compare/1689897600/1690848000

21 keys

Item 6

https://backpack.tf/item/4277001548

Sale 7

https://backpack.tf/profiles/76561199192607141#!/compare/1683590400/1683676800

https://backpack.tf/profiles/76561198139444147#!/compare/1683590400/1683676800

Can only match a handful of keys, not too sure here (17 on buyer side but that seems incomplete still)

Item 7

https://backpack.tf/item/4268242136

This looks like just bot transfers

Mp.tf

https://marketplace.tf/items/tf2/30672;5;u3088

$79.99 / $2.03 = ~39 keys (May 13)

$79.99 / $1.98 = ~40 keys (Jul 2)

$69.99 / $1.95 = ~36 keys (Jul 30)

$74.99 / $1.95 = ~38 keys (Aug 2)

Total Sales

18, 21, 25, 28, 36, 38, 39, 40

https://imgur.com/a/bOmBzG2

Multiple buyers above 21

Sellers on mp.tf below 39 / 40

25 is relatively close to buyers as well, so to tighten the range a bit, I'll go with 28 - 38 keys c: