Sale #1:

https://backpack.tf/profiles/76561198056180801#!/compare/1555545600/1555632000

Bulk.

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Sale #2:

https://backpack.tf/profiles/76561198264117106#!/compare/1555718400/1555804800

Sold for 29 keys.

29 keys

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Sale #3:

https://backpack.tf/profiles/76561198007953976#!/compare/1555113600/1555200000

Bulk.

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Sale #4:

https://backpack.tf/profiles/76561198317061799#!/compare/1555459200/1555632000

Bulk.

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Sale #5:

https://backpack.tf/profiles/76561198061489334#!/compare/1549670400/1549756800

Sold for 5 keys and a Circling TF Logo Tyrantium Helmet (24 keys)

29 keys

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Sale #6:

https://backpack.tf/profiles/76561198220052159#!/compare/1549843200/1549929600

Sold for 21 keys.

21 keys

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Marketplace.tf stats:

https://marketplace.tf/items/30004;5;u29

Past 90 days:

1x $56 ($56 / $1.80 = ~31 keys)

1x $57 ($57 / $1.78 = ~32 keys) [B/O was 29 keys (https://bot.tf/stats/listings/4R61DOEM)]

Sales:

21, 29, 29, 29, 31. Going with 29 - 31 keys.