Sale 1:

https://backpack.tf/profiles/76561198304138933#!/compare/1529020800/1529107200

https://backpack.tf/profiles/76561198238947798#!/compare/1528502400/1529107200

Keys, untraceable.

Sale 2:

https://backpack.tf/profiles/76561198109727272#!/compare/1528675200/1528761600

https://backpack.tf/profiles/76561198831310970#!/compare/1528329600/1528761600

SCM Sale.

https://steamcommunity.com/market/listings/440/Unusual%20Brain%20Bucket

Sold for 72.33 CAD

Keys at 3.08 CAD

Total is 23.48 keys

Sale 3:

https://backpack.tf/profiles/76561198831310970#!/compare/1529884800/1530403200

https://backpack.tf/profiles/76561198111137125#!/compare/1528588800/1530316800

Untrace.

Sale 4:

https://backpack.tf/profiles/76561198114286047#!/compare/1530403200/1531008000

Low, but cannot confirm if there was more due to being unable to update the backpacks.

Sale 5, 6, 7:

https://backpack.tf/profiles/76561198114286047#!/compare/1530403200/1531008000

All three sold for 49.99 USD

Keys were at 1.94, 1.94, 1.97

Totals are 25.77, ~25.77, 25.38 keys

Considering sellers:

https://i.imgur.com/5oniyDy.jpg

Rounding 25 .77 down to 25,

taking 23 - 25.