Sale 1:

Sold for 11 keys in ~1 month

http://www.tf2outpost.com/trade/28797552 - B/O of 11.5 (only outpost trade I could find, was a fair bit before the sale, price probably lowered afterwards)

Seller: http://backpack.tf/profiles/76561198002757046#!/compare/1488412800/1488499200

Buyer: http://backpack.tf/profiles/76561198124241068#!/compare/1488240000/1488499200

X = 11

Sale 2:

Sold for 11 keys in ~2 days

http://www.tf2outpost.com/trade/28841494 - B/O of 12

Seller: http://backpack.tf/profiles/76561198072819916#!/compare/1490140800/1490227200

Buyer: http://backpack.tf/profiles/76561198303776039#!/compare/1490140800/1490227200

X = 11

Sale 3:

Sold for 10 keys + <0.5 keys in metal/items in ~3 days

http://www.tf2outpost.com/trade/28837708 - Deleted B/O

Seller: http://backpack.tf/profiles/76561198044335614#!/compare/1489968000/1490054400

Buyer: http://backpack.tf/profiles/76561198072819916#!/compare/1489968000/1490054400

X = 10

Sale 4:

Bulk for Burning Magistrate’s Mullet

Seller: http://backpack.tf/profiles/76561198296076323#!/compare/1492473600/1492819200

Buyer: http://backpack.tf/profiles/76561198082745608#!/compare/1492732800/1492819200

Sellers:

11 keys:

http://i.imgur.com/p6snjPw.png - 3 days

http://backpack.tf/u/76561198220428932

http://www.tf2outpost.com/trade/28904259

12 keys:

http://i.imgur.com/g6voIMD.png - 18 days

http://backpack.tf/u/76561198012613726

http://www.tf2outpost.com/trade/28822445

Sales at:

10

11 (2x)

Not excluding 11, as there are no sales for higher, one of the sales took about a month, and there’s another seller at 11 right now. 11 seems to be a common trading point. Will exclude 10, however.

Going with 11 flat.