Sale #1:

https://backpack.tf/profiles/76561198391320101#!/compare/1552003200/1552089600

Unsure.

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Sale #2:

https://backpack.tf/profiles/76561198391320101#!/compare/1552089600/1552176000

Untraceable.

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Sale #3:

https://bot.tf/stats/item?def=338&q=5&ef=Smoking&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198358778649#!/compare/1548370800/1548457200

Bought for 10 keys and 2.33 ref.

10 keys

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Sale #4:

https://bot.tf/stats/item?def=338&q=5&ef=Smoking&craft=1&aus=0&ks=0

https://backpack.tf/profiles/76561198358778649#!/compare/1552172400/1552258800

Bought for 10 keys and 6.44 ref.

10 keys

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Sale #5:

https://marketplace.tf/items/338;5;u35

Sold for $25.46.

$25.46 / $1.80 = ~14 keys

14 keys

Sales:

10, 10, 14. Going with 10 - 14 keys.