Credits to Explocivo808 for the previous suggestion.

Marketplace.tf Sales

https://marketplace.tf/items/tf2/1106;5;u3014

MP.TF Sale #1

Sold for $69.99 on May 18, 2023

Keys @ $2.02

69.99/2.02 = 34.65ish keys

MP.TF Sale #2

Sold for $40 on July 26, 2023

Keys @ $1.95

40/1.95 = 20.51ish keys

MP.TF Sale #3

Sold for $50 on August 8th, 2023

Keys @ $2.04

50/2.04 = 24.51ish keys

Sales @ 21, 35, 25

With a new sale right in the middle of the other 2 previous sales, makes sense to include the higher on now. Taking 21-35 keys.