I think this is, single-handedly, the most stable unusual of all time.

Sold for 10 Keys

http://backpack.tf/profiles/76561198023542389/#!/compare/1460073600/1460160000

Sold for 4.5 Keys and ~5.5 Keys in Sweets(10 Keys total)

http://backpack.tf/profiles/76561198023542389/#!/compare/1455782400/1455868800

Sold for ~10 Keys in Items

http://backpack.tf/profiles/76561198108322287/#!/compare/1458864000/1458950400

Sold for an Australium Frontier Justice(11 Keys)(Item IDs match)(B/O was 10)

http://backpack.tf/profiles/76561198036177506/#!/compare/1454832000/1455350400

http://www.tf2outpost.com/trade/2781618

Sold for 8 Keys(1 Key was in metal) and ~2 Keys in Sweets(10 Keys total)

http://backpack.tf/profiles/76561198205383525/#!/compare/1458111600/1458198000

Five sales, 10 Keys should be fine.

Additional Proof/Counter-Proof/Constructive Criticism/Feedback is always appreciated.