Sale 1:

Sold for Bubbling Larrikin Robin

http://www.tf2outpost.com/trade/27827124 - B/O of 11, Seller confirms trade (legend)

Seller: http://backpack.tf/profiles/76561198031371895/#!/compare/1455782400/1455868800

Buyer: http://backpack.tf/profiles/76561198138476703/#!/compare/1453536000/1455868800

Larrikin Robin cannot be less than 11, due to buyers at 10:

http://www.tf2outpost.com/trade/27957244

http://www.tf2outpost.com/trade/26576672

http://www.tf2outpost.com/trade/27760190

http://www.tf2outpost.com/trade/27951289

http://www.tf2outpost.com/trade/27958317

X = 11 (Capped by B/O)

Sale 2:

Sold for Orbiting Planets Berliner's Bucket Helm

http://www.tf2outpost.com/trade/27874372 - B/O of 10

Seller: http://backpack.tf/profiles/76561198031007256/#!/compare/1455955200/1456041600

Buyer: http://backpack.tf/profiles/76561198021808164/#!/compare/1455955200/1456041600

Bucket helm can not be less than 10, due to buyers at 9

http://puu.sh/nIjuJ/9f47c0b599.png

X = 10 (Capped by B/O)

Sale 3:

Sold not long after acquiring it to a buyer for 9 keys

No outpost link available

Seller: http://backpack.tf/profiles/76561198146671092/#!/compare/1457596800/1458025200

Buyer: http://backpack.tf/profiles/76561198002757046/#!/compare/1457510400/1457596800

X = 9

Sale 4:

Sold in less than a day for 8 keys

http://www.tf2outpost.com/trade/27865964 - Offers

Seller: http://backpack.tf/profiles/76561198138476703/#!/compare/1455868800/1455955200

Buyer: http://backpack.tf/profiles/76561198031007256/#!/compare/1455868800/1455955200

X = 8

Sale 5:

Sold for Stormy Storm Headwarmer

No outpost link available

Seller: http://backpack.tf/profiles/76561198068311804/#!/compare/1452585600/1458025200

Buyer: http://backpack.tf/profiles/76561198067692882/#!/compare/1452153600/1454572800

X = 16

Sale 6:

Sold for junk

No outpost link available

Seller: http://backpack.tf/profiles/76561198021808164/#!/compare/1456041600/1457769600

Buyer: http://backpack.tf/profiles/76561198146671092/#!/compare/1457510400/1457596800

Best not to use a sale like this

Sellers:

10 keys:

http://puu.sh/nIiVq/0978dd1c62.png - 5 days

11 keys:

http://www.tf2outpost.com/trade/27941056 - 5 days

http://puu.sh/nIiWP/406c59fcbc.png 2 unique sellers, both unbumped

Buyers:

8 keys:

http://www.tf2outpost.com/trade/27952726

http://www.tf2outpost.com/trade/27934308

http://www.tf2outpost.com/trade/26827781

http://www.tf2outpost.com/trade/27167163

http://www.tf2outpost.com/trade/27841601

8.3 key:

http://www.tf2outpost.com/trade/27961003

http://www.tf2outpost.com/trade/27915191

Sales at:

8 (quicksale)

9 (quicksale)

10

11

16

Calling 16 an outlier

Going with 10-11