Sale 1:

Sold for 12 keys

http://www.tf2outpost.com/trade/28089343 - B/O of 12

Seller: http://backpack.tf/profiles/76561198197828049#!/compare/1460937600/1461024000

Buyer: http://backpack.tf/profiles/76561198002757046#!/compare/1460937600/1461024000

X = 12

Sale 2:

Sold for 11 keys

http://www.tf2outpost.com/trade/28254450 - B/O of 11

Seller: http://backpack.tf/profiles/76561198057172126#!/compare/1465862400/1465948800

Buyer: http://backpack.tf/profiles/76561198209582564#!/compare/1465862400/1465948800

X = 11

Sale 3:

Sold for 11 keys

No outpost

Seller: http://backpack.tf/profiles/76561198209582564#!/compare/1466380800/1466467200

Buyer: http://backpack.tf/profiles/76561198092471230#!/compare/1466208000/1466467200

X = 11

Sale 4:

Sold for 10 keys + Strange Festive Killstreak Frontier Justice + 3 ref

No outpost

Seller: http://backpack.tf/profiles/76561198092471230#!/compare/1466208000/1466467200

Buyer: http://backpack.tf/profiles/76561198055778504#!/compare/1466380800/1466467200

X = 11

Sale 5:

Sold for 10 keys + ~1 key in items

http://www.tf2outpost.com/trade/28275896 - B/O of 11.5, Declined 10

Seller: http://backpack.tf/profiles/76561198055778504#!/compare/1466812800/1466899200

Buyer: http://backpack.tf/profiles/76561198056961724#!/compare/1466812800/1466899200

X = 11

Sale 6:

Sold for 10 keys

http://www.tf2outpost.com/trade/28251906 - B/O of 14

Seller: http://backpack.tf/profiles/76561198055224435#!/compare/1465689600/1465776000

Buyer: http://backpack.tf/profiles/76561198057172126#!/compare/1465689600/1465776000

X = 10

Sellers:

12 keys:

http://www.tf2outpost.com/trade/28287310 - young

http://puu.sh/pGjUu/4383c73f16.png - 4 days

13 keys:

http://puu.sh/pGjVL/8a74fa6e3d.png - 2 months

Sales at:

10

11

11

11

11

12

10 looks kinda low, especially since an offer of 10 keys was declined

Not going to ignore 12, because full pure

Going with 11-12