Classifieds at the time of posting this suggestion.

The age of the listing(s) are shown in the screenshots rather than the last bump - Unsolds and item histories are presented in chronological order according to the screenshot(s).

x2 for sale at 5.3 Keys - http://i.imgur.com/texSwLj.png

Unsold for 1 day http://backpack.tf/item/640556451

Unsold for 2 days http://backpack.tf/item/643926275

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x2 for sale at 5.65 Keys - http://i.imgur.com/PByGjwl.png

Unsold for 5 days http://backpack.tf/item/629519963

Unsold for 3 days http://backpack.tf/item/621083408

Outpost sellers.

http://www.tf2outpost.com/trade/28384377 - 5.7 Keys - Unsold for 1 month.

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http://www.tf2outpost.com/trade/28454152 - ~5.7 Keys(Duplicated).

Item has switched hands but > http://backpack.tf/profiles/76561198040892342#!/compare/1472601600/1472688000 ???

Discounting.

I am excluding all trades on Outpost that haven't been bumped for 1 day or more.