Sale 1: ~15 Keys Pure.

https://backpack.tf/profiles/76561198048851745#!/compare/1551225600/1551312000

https://backpack.tf/profiles/76561198025374641#!/compare/1550016000/1551312000

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Sale 2: Untrace.

https://backpack.tf/profiles/76561198025374641#!/compare/1552608000/1552694400

https://backpack.tf/profiles/76561198121830870#!/compare/1552521600/1552608000 (keys history doesn't match)

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Marketplace.tf Sales:

https://marketplace.tf/items/30939;5;u59

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Sale 3: ~16 Keys.

Apr 11

$28.99 / $1.77 = 16.38 keys

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Usable Sales: 15.16

Going with 15-16 keys.

Thanks to scourge for the premium!