Sale 1:

https://backpack.tf/profiles/76561198326254870#!/compare/1582502400/1583020800

https://backpack.tf/profiles/76561198197292179#!/compare/1582848000/1583107200

Bulk

sale 2:

https://backpack.tf/profiles/76561198361087694#!/compare/1581897600/1583884800

https://backpack.tf/profiles/76561198088137554#!/compare/1580947200/1581897600

Bulky

sale 3:

https://backpack.tf/profiles/76561198088137554#!/compare/1582588800/1582675200

https://backpack.tf/profiles/76561198318065526#!/compare/1582588800/1582675200

Sold for 15 keys

sale 4:

https://backpack.tf/profiles/76561198318065526#!/compare/1583625600/1583712000

https://backpack.tf/profiles/76561198095553478#!/compare/1583625600/1583712000

Sold for OF Pithy + ~5 keys in sweets

use there

sale 5:

https://backpack.tf/profiles/76561198095553478#!/compare/1583798400/1583884800

https://backpack.tf/profiles/76561199011873091#!/compare/1583798400/1583884800

Sold with 1 key for Aces Boxcar

Boxcar Mini:

https://backpack.tf/suggestion/5ea8ffa52ff31c586675abed

Suggestion for 15 keys

Total is 14 keys

sale 6:

https://backpack.tf/profiles/76561199011873091#!/compare/1583884800/1583971200

https://backpack.tf/profiles/76561198305494036#!/compare/1583971200/1584057600

QS

sale 7:

https://backpack.tf/profiles/76561198305494036#!/compare/1584230400/1584316800

https://backpack.tf/profiles/76561198097271466#!/compare/1584230400/1584316800

Bulk for keys

sale 8:

https://backpack.tf/profiles/76561198097271466#!/compare/1587168000/1587254400

https://backpack.tf/profiles/76561198281630040#!/compare/1587168000/1587254400

Sold for 15 keys

sale 9:

https://marketplace.tf/items/tf2/30034;5;u8

$28.1 / $1.77 = 15.88 keys <--- https://backpack.tf/item/7956395262

$30 / $1.79 = 16.76 keys <--- https://backpack.tf/item/7956395262

Total sales @:

14, 15, 15, 16, 17 keys

one buyer up to ~13.75 keys,

taking 15 - 17 keys.