Sale 1:

https://backpack.tf/profiles/76561198260201158#!/compare/1571097600/1571184000

https://backpack.tf/profiles/76561198087531087#!/compare/1571184000/1571270400

Sold for 13 keys

sale 2:

https://backpack.tf/profiles/76561198087531087#!/compare/1573776000/1573862400

https://backpack.tf/profiles/76561198035109737#!/compare/1573776000/1573862400

Sold for ~11 keys

Sale 3:

https://backpack.tf/profiles/76561198035109737#!/compare/1573862400/1573948800

https://backpack.tf/profiles/76561198286257338#!/compare/1573862400/1573948800

Sold for 11 keys

sale 4:

https://backpack.tf/profiles/76561198286257338#!/compare/1573948800/1574035200

https://backpack.tf/profiles/76561198145314530#!/compare/1573948800/1574035200

Sold for spell

Sale 5:

https://backpack.tf/profiles/76561198415625616#!/compare/1571356800/1571443200

https://backpack.tf/profiles/76561198454615761#!/compare/1571356800/1571443200

QS

sale 6:

https://backpack.tf/profiles/76561198454615761#!/compare/1572566400/1572652800

https://backpack.tf/profiles/76561198064629474#!/compare/1571702400/1572652800

Keys

sale 7:

https://backpack.tf/profiles/76561198298140322#!/compare/1572912000/1572998400

https://backpack.tf/profiles/76561198125791160#!/compare/1572912000/1572998400

Sold for CPS Titanium

use there

Sale 8:

https://backpack.tf/profiles/76561198125791160#!/compare/1573516800/1573603200

https://backpack.tf/profiles/76561198404491245#!/compare/1573516800/1573603200

Sold for 14 keys

sale 6:

https://backpack.tf/profiles/76561198105488946#!/compare/1570924800/1571270400

https://backpack.tf/profiles/76561198145314530#!/compare/1570924800/1571011200

Sold for 12 keys

sale 7:

https://backpack.tf/profiles/76561198145314530#!/compare/1571788800/1571875200

https://backpack.tf/profiles/76561198002757046#!/compare/1571702400/1571788800

Bulk

sale 8:

https://backpack.tf/profiles/76561198002757046#!/compare/1571875200/1571961600

https://backpack.tf/profiles/76561198072811851#!/compare/1571961600/1572048000

Sold for 13 keys

Sale 9:

https://backpack.tf/profiles/76561198072811851#!/compare/1572220800/1572393600

https://backpack.tf/profiles/76561198454615761#!/compare/1572307200/1572393600

QS

Sale 10:

https://marketplace.tf/items/tf2/1111;5;u3021

$19.05 / $1.82 = 10.47 keys <--- https://backpack.tf/item/3928136464

Total sales 2:

10.47, 11, 11, 12, 13, 13, 14 keys

buyers up to ~10.5 keys,

sellers down to 15 keys,

taking 11 - 14 keys