Classifieds at the time of posting this suggestion.

The age of the listing(s) are shown in the screenshot(s) rather than the last bump.

Unsolds and item histories are presented in chronological order according to the screenshot(s).

x1 for sale at 1.35 Keys - http://i.imgur.com/uuWOwcJ.png

Unsold for 11 days http://backpack.tf/item/4274681978

Outpost sellers.

http://www.tf2outpost.com/trade/28448783 - 1.5 Keys - Unsold for 2 weeks.

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