Sale 1:

Sold with 3 keys for Pro. KS Aussie Black Box (21)

No outpost

Seller: http://backpack.tf/profiles/76561198157493895#!/compare/1482019200/1482105600

Buyer: http://backpack.tf/profiles/76561198338556449#!/compare/1482105600/1482192000

X = 18

Sale 2:

Sold for Bubbling Noble (Mini at 17.5 below)

No outpost

Seller: http://backpack.tf/profiles/76561198102158246#!/compare/1477008000/1477094400

Buyer: http://backpack.tf/profiles/76561198165504020#!/compare/1477008000/1477094400

X = 18

Sale 3:

Sold for Orbiting Fire Air Dog (Mini at 17 below) + ~1 key in items

No outpost

Seller: http://backpack.tf/profiles/76561198243530442#!/compare/1476921600/1477008000

Buyer: http://backpack.tf/profiles/76561198102158246#!/compare/1476921600/1477008000

X = 18

Bubbling Noble Mini:

http://backpack.tf/suggestion/586a210a0e2cad758776be91

Orbiting Fire Air Dog Mini:

Sold for Tesla Coil Wide-Brimmed Bandito (18.5) + 5 keys

http://www.tf2outpost.com/trade/28632575 - B/O of 18

Seller: http://backpack.tf/profiles/76561197997146443#!/compare/1480377600/1480464000

Buyer: http://backpack.tf/profiles/76561198131988947#!/compare/1480291200/1480464000

X = 18 (Capped by B/O)

And the seller of Sale 3 is re-selling for 16:

http://i.imgur.com/V9gIQ2o.png

http://backpack.tf/u/76561198243530442

Going with 16-18 (17) for the Orbiting Fire Air Dog

Sellers:

22 keys:

http://i.imgur.com/iSbaifr.png

http://backpack.tf/u/76561198037360212

Sales at:

18 (3x)

Going with 18 flat.