Item 1

https://backpack.tf/item/16985917365

https://marketplace.tf/items/tf2/30120;5;u57

$39.99

https://marketplace.tf/items/tf2/5021;6 - taking $1.93/key

~20.72 keys

Item 2 (very close to 3 months old)

https://backpack.tf/item/5933902039

https://backpack.tf/profiles/76561198802228414#!/compare/1773446400/1773792000 (https://next.backpack.tf/profiles/76561198802228414/compare?from=1773446400&to=1773792000)

https://backpack.tf/profiles/76561199072611396#!/compare/1773360000/1773446400

15 keys 18.33 ref

Item 3

https://backpack.tf/item/16916240553

https://backpack.tf/profiles/76561198338522254#!/compare/1779408000/1779494400 (https://next.backpack.tf/profiles/76561198338522254/compare?from=1779408000&to=1779494400)

https://backpack.tf/profiles/76561199389274250#!/compare/1779408000/1779494400 (https://next.backpack.tf/profiles/76561199389274250/compare?from=1779408000&to=1779494400)

Bot dump for 14 keys 51.88 ref

https://ibb.co/SD05j7Zq

https://ibb.co/r26Y1ZCc - 56.77-57 ref/key

Unsolds

https://ibb.co/FdqxgXk - 22 keys for 3 months

https://backpack.tf/item/2397129716 - $39.99 for 9 months (estimate; not cross-listed 1 month ago)

Others

https://ibb.co/216bCwzj - Clone's SCM listing, reference only

$42.00 / 16.79 keys

Using bot dump as the lower bounding end

Taking 15-21 keys after rounding