Sale 1:

https://backpack.tf/profiles/76561198051707681#!/compare/1547164800/1549929600

https://backpack.tf/profiles/76561198135388328#!/compare/1547164800/1552348800

(Couldn't trace)

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Sale 2:

https://backpack.tf/profiles/76561198123959574#!/compare/1547164800/1547251200

https://backpack.tf/profiles/76561198135388328#!/compare/1547164800/1547424000 (Nothing here)

(Couldn't trace)

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Sale 3:

https://backpack.tf/profiles/76561198123959574#!/compare/1547251200/1547424000

https://backpack.tf/profiles/76561198211566865#!/compare/1547251200/1547337600

(Couldn't trace)

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Sale 4:

https://backpack.tf/profiles/76561198211566865#!/compare/1549152000/1549238400

https://backpack.tf/profiles/76561198038751912#!/compare/1549152000/1549238400

Strange Australium Knife (Lowest Sell Order 18.2 Keys)+ 3 Tour of Duty Ticket (Lowest Sell Order 22.22X3=66.66ref ~1.47)+ 1 Non-Craftable Tour of Duty Ticket (Lowest Sell Order 21ref)

~18.2 keys+ 1.47 keys + 0.46 Keys=20.13

~20 Keys

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Sale 5:

https://backpack.tf/profiles/76561198038751912#!/compare/1549065600/1549843200

https://backpack.tf/profiles/76561198311498888#!/compare/1549152000/1549411200

https://imgur.com/OYrZBoj

(Couldn't trace)

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Sale 6:

https://backpack.tf/profiles/76561198006544512#!/compare/1551398400/1551484800

https://backpack.tf/profiles/76561198083901071#!/compare/1551312000/1551484800

(Couldn't trace)

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Sale 7:

https://backpack.tf/profiles/76561198083901071#!/compare/1551398400/1551484800

https://backpack.tf/profiles/76561198305494036#!/compare/1551398400/1551484800

Around 19 keys (Quick Sell)

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Sale 8:

https://backpack.tf/profiles/76561198305494036#!/compare/1553299200/1553472000

https://backpack.tf/profiles/76561198445049721#!/compare/1553299200/1553472000

(Couldn't trace)

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Sale 9:

https://backpack.tf/profiles/76561198445049721#!/compare/1553299200/1553472000

https://backpack.tf/profiles/76561198181484402#!/compare/1553299200/1553472000

(Couldn't trace)

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Sale 10:

https://backpack.tf/profiles/76561198181484402#!/compare/1553472000/1553644800

https://backpack.tf/profiles/76561198298223499#!/compare/1553385600/1553731200

(Couldn't trace)

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Sale 11:

https://backpack.tf/profiles/76561198006544512#!/compare/1547942400/1548028800

https://backpack.tf/profiles/76561197979945840#!/compare/1547942400/1548028800

(Couldn't trace)

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Sale 12:

https://backpack.tf/profiles/76561198006544512#!/compare/1553558400/1553731200

https://backpack.tf/profiles/76561197979945840#!/compare/1548028800/1553558400

(Couldn't trace)

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Sale 13

https://backpack.tf/profiles/76561198006544512#!/compare/1553644800/1553731200

https://backpack.tf/profiles/76561198128550841#!/compare/1553644800/1553731200

(Couldn't trace)

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Sale 14:

https://backpack.tf/profiles/76561198168863803#!/compare/1546732800/1546819200

https://backpack.tf/profiles/76561198368461164#!/compare/1546732800/1546819200

~22 Keys Pure

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Sale 15:

https://backpack.tf/profiles/76561198368461164#!/compare/1546732800/1546819200

https://backpack.tf/profiles/76561198857718016#!/compare/1546732800/1546819200

(Couldn't trace)

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Sale 16:

https://backpack.tf/profiles/76561198857718016#!/compare/1546732800/1550102400

https://backpack.tf/profiles/76561198876258432#!/compare/1549324800/1549497600

(Couldn't trace)

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Sale 17:

https://backpack.tf/profiles/76561198431663881#!/compare/1552608000/1552867200

https://backpack.tf/profiles/76561198148271375#!/compare/1547769600/1547856000

(Couldn't trace)

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Sale 18:

https://backpack.tf/profiles/76561198175420885#!/compare/1551916800/1552089600

https://backpack.tf/profiles/76561198337734785#!/compare/1551916800/1552089600

(Couldn't trace)

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Sale 19:

https://marketplace.tf/items/180;5;u58

Price on this day: $1.8

$50.00 / $1.8 = 27.78 keys

~28 Keys

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Sale 20:

https://backpack.tf/profiles/76561198431135206#!/compare/1551571200/1551744000

https://backpack.tf/profiles/76561198175420885#!/compare/1551657600/1551744000

(Bulk)

Sales 20,22,28.

Sellers at 20.

Going With 20-28