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 1 Key - http://i.imgur.com/DA0NKEo.png

Unsold for 16 days http://backpack.tf/item/3609066997

Unsold for 18 days http://backpack.tf/item/4475521943

Every other seller is for 1.15 Keys, 6 of them same seller, other 2 is from 1 seller.

http://i.imgur.com/2nzs9bL.png.

Outpost sellers.

http://www.tf2outpost.com/trade/16148532 - 1 Key - 2 Year old seller, presumed consistently stocked.

Fun fact: The item in the trade is still in the sellers inventory, 2 year old trade.

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