Taking 3 offers that fit this range.

Item #1

Sale: 1

Owner says he got it for 60 pure. Likely, as compare shows 59. Either way, perfectly fits the range.

https://backpack.tf/profiles/76561199125443371#!/compare/1637539200/1637712000

https://backpack.tf/profiles/76561198067435035#!/compare/1637452800/1637798400

Item #2

https://backpack.tf/item/11189720065

Sale 1:

Bought on Mannco for $90 on 11th Dec.

https://backpack.tf/profiles/76561198834107391#!/compare/1638835200/1639526400

https://backpack.tf/profiles/76561198177146103#!/compare/1638662400/1638921600

https://mannco.store/item/440-death-at-dusk-unusual-mann-of-reason

Key prices on 11th Dec. were $1.64 (5-day average is 1.64 - 1.64/1.65/1.64/1.64/1.63)

https://mannco.store/item/440-mann-co-supply-crate-key

90/1.64 = 54.87804... Rounding up to 55.

Sale #2

Bought for 65 keys pure.

https://backpack.tf/profiles/76561198248209800#!/compare/1642291200/1642377600

https://backpack.tf/profiles/76561198177146103#!/compare/1642204800/1642377600

60, 55, 65. Taking 55-65