Sale 1:

https://backpack.tf/profiles/76561198839597104#!/compare/1626048000/1626220800

https://backpack.tf/profiles/76561199085116273#!/compare/1626048000/1626134400

?

Sale 2:

https://backpack.tf/profiles/76561199085116273#!/compare/1626220800/1626307200

https://backpack.tf/profiles/76561198280524116#!/compare/1626220800/1626307200

idk

Sale 3:

https://backpack.tf/profiles/76561198401343981#!/compare/1631577600/1631750400

either 7 keys 15 refs or 9 keys 2 refs cuz same user dumped 2 hats to stn.tf (this and bubbling buckaroos)

Sale 4, 5 and 6 are marketplace sales

key prices

3x17.99$

Jun 26 - Jul 31 - Sep 11

One of the histories could be this: https://backpack.tf/item/8415621964

Jun 26 sale equals 17.99/1.85=9.72 keys, which is closer to 9.5 than 10.

Jul 31 sale equals 17.99/1.81=9.93 keys which is 10 keys

Sep 11 sale equals 17.99/1.84=9.77 keys which is closer to 10 keys

So I'm going with 9.5-10 keys range.