Resuggestion from https://backpack.tf/suggestion/5ed8c063ef11181b463444a1

None of the proof is mine, so I am copy pasting the relevant information as-is:

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Proof by https://backpack.tf/u/76561198137566942

Was only gonna make a mini on this, but look at all the pure sales :o

https://backpack.tf/profiles/76561198160856661#!/compare/1584057600/1584144000

Sold for 44 keys.

https://backpack.tf/profiles/76561198190714350#!/compare/1583712000/1583798400

Sold for 42 keys.

https://backpack.tf/profiles/76561198415525729#!/compare/1587859200/1587945600

Sold for 43 keys.

https://backpack.tf/profiles/76561198003977258#!/compare/1586563200/1587859200

Sold for 41 keys.

https://backpack.tf/profiles/76561198061779536#!/compare/1587168000/1587254400

Sold for 57 keys.

https://backpack.tf/profiles/76561198059874094#!/compare/1586736000/1586908800

Sold for 42 keys + ~7 ref sweets.

https://backpack.tf/profiles/76561198059874094#!/compare/1586649600/1586736000

Sold for 41 keys.

https://marketplace.tf/items/tf2/359;5;u9

Duped sold for 79.99$ = ~47 keys.

https://backpack.tf/item/276285012

No b/o found.

Sold for 99.99$ = ~53 keys.

No history found.

No b/o found.

Sales we have:

41 x2

42 x2

43 x1

44 x1

47 x1

53 x1

57 x1

57 might seem a bit high considering the unsolds, so i'm gonna include 41 to balance it out a bit.

57 sold within a day i might add.

Going with 41-57 keys.

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Proof by https://backpack.tf/u/76561198085880346

https://backpack.tf/item/1797140726 - History for the $99.99 sale

The sale for 43 Keys is the same as the sale for 41 Keys directly below it (it wasn't 43 Keys).

https://backpack.tf/profiles/76561198280667527#!/compare/1586736000/1586908800 - DBD Casemaker (37 Keys) + 1 Key + ~1 Key of Items

https://backpack.tf/profiles/76561198131362066#!/compare/1587081600/1587168000 - Better for the Caribou

https://backpack.tf/profiles/76561198031010329#!/compare/1587340800/1587600000 - Bulk sale

https://backpack.tf/profiles/76561198048724906#!/compare/1592870400/1592956800 - ?

https://marketplace.tf/items/tf2/359;5;u9 - Sold again for $99.99 (50 Keys). Don't know the history.

https://imgur.com/a/Q7zvhJy - Sellers at 48 and 51 Keys

https://backpack.tf/item/7956803883

https://backpack.tf/item/404587069

I'd narrow the range to 42 - 53 Keys. Also, take a picture of the sellers + link their histories in the future in case they sell.

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Going with 42-53 keys