Sale 1:

https://backpack.tf/profiles/76561198157196963#!/compare/1527379200/1527465600

https://backpack.tf/profiles/76561197972180709#!/compare/1527465600/1528416000

Sold for Aussie Amby(~13)

Sale 2:

https://backpack.tf/profiles/76561198353418874#!/compare/1530835200/1530921600

https://backpack.tf/profiles/76561198232041512#!/compare/1530835200/1530921600

Sold for Isotope BS Quack Rocket Launcher

RL Mini:

https://backpack.tf/suggestion/5b5a497244325a56053e8309

Suggestion for 40 keys.

Sale 3:

https://backpack.tf/profiles/76561198232041512#!/compare/1530835200/1530921600

https://backpack.tf/profiles/76561198176297517#!/compare/1530662400/1530921600

Sold for TFL Tyrannus(17)

Sale 4:

https://backpack.tf/profiles/76561198176297517#!/compare/1531526400/1531612800

https://backpack.tf/profiles/76561198301015840#!/compare/1531526400/1531612800

Untrace.

Sale 5:

https://backpack.tf/profiles/76561198318622241#!/compare/1527465600/1527811200

https://backpack.tf/profiles/76561198002757046#!/compare/1527724800/1527811200

Sold for 14 keys

Sale 6:

https://backpack.tf/profiles/76561198002757046#!/compare/1527811200/1527897600

https://backpack.tf/profiles/76561198051011524#!/compare/1527811200/1527897600

Untrace, keys.

Sale 7:

https://backpack.tf/profiles/76561198051011524#!/compare/1529280000/1529539200

https://backpack.tf/profiles/76561198121830870#!/compare/1529452800/1529539200

Untrace.

Sale 8:

https://backpack.tf/profiles/76561198121830870#!/compare/1531267200/1531353600

https://backpack.tf/profiles/76561198262802628#!/compare/1531008000/1531699200

Untrace.

Sale 9:

https://backpack.tf/profiles/76561198262802628#!/compare/1531872000/1531958400

https://backpack.tf/profiles/76561198080179568#!/compare/1531872000/1531958400

Bulk.

Total sales @:

13, 14, 17, 40

40 is outlier, obviously.

Lets go with 14-17 keys, as I believe Rubi has a hidden buy order for 14.