The one currently listed on outpost has numerous pure offers above this. Closing.

http://www.tf2outpost.com/trade/27908872

yeah, agreed. Especially since he sold in like a day.

There's also this, but not sure what exactly it sold for due to the buyers bp gap

http://www.tf2outpost.com/trade/27984057

http://backpack.tf/profiles/76561198113673803/#!/compare/1458777600/1458950400

http://backpack.tf/profiles/76561198061516523/#!/compare/1457769600/1459641600

"28 key offer", Id have taken that as 28 pure if it wasnt for his 27 buyout. so meh, idk. but 21 is too low for sure. Youll need to wait until the current one sells and suggest at that value, completely excluding 21