Sale #1:

https://backpack.tf/profiles/76561198083134207#!/compare/1548460800/1548547200

Bought for 19 keys.

19 keys

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Sale #2:

https://backpack.tf/profiles/76561198083134207#!/compare/1549497600/1549584000

Bought for 18 keys and 10 ref.

18 keys

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Sale #3:

https://backpack.tf/profiles/76561198121830870#!/compare/1548028800/1548115200

Bought for 18 keys.

18 keys

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Sale #4:

https://backpack.tf/profiles/76561198121830870#!/compare/1549238400/1549324800

Sold for 20 keys.

20 keys

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Sale #5:

https://backpack.tf/profiles/76561198156570751#!/compare/1549411200/1549497600

Untraceable.

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Sale #6:

https://backpack.tf/profiles/76561198039558598#!/compare/1549411200/1549497600

Untraceable.

Sales:

18, 18, 19, 20. Going with 19 - 20 keys, quickbuyers start at 18 keys.