Sale 1:

Sold for Dead Presidents Old Guadalajara (12) + Spec. KS Aussie (7)

No outpost

Seller: https://backpack.tf/profiles/76561198259000762#!/compare/1503792000/1504051200

Buyer: https://backpack.tf/profiles/76561198276474157#!/compare/1503964800/1504051200

X = 19

Sale 2:

Sold for 15 keys

No outpost

Seller: https://backpack.tf/profiles/76561198316071886#!/compare/1501977600/1502064000

Buyer: https://backpack.tf/profiles/76561198137130509#!/compare/1501977600/1502064000

X = 15

Sale 3:

Sold for 15 keys

No outpost

Seller: https://backpack.tf/profiles/76561198061440669#!/compare/1501200000/1501286400

Buyer: https://backpack.tf/profiles/76561198145575631#!/compare/1501200000/1501286400

X = 15

Sale 4:

Sold for Steaming El Jefe (16.5) + 1 key

http://www.tf2outpost.com/trade/29355908 - B/O of 14

Seller: https://backpack.tf/profiles/76561198064423172#!/compare/1504915200/1505001600

Buyer: https://backpack.tf/profiles/76561198061684027#!/compare/1504915200/1505001600

X = 14 (Capped by B/O)

Sale 5:

Sold for 14 keys + 1 ref

http://www.tf2outpost.com/trade/29334233 - B/O of 15

Seller: https://backpack.tf/profiles/76561198128939937#!/compare/1503705600/1503792000

Buyer: https://backpack.tf/profiles/76561198259000762#!/compare/1503619200/1503792000

X = 14

Sale 6:

Quicksold for 13 keys

No outpost

Seller: https://backpack.tf/profiles/76561198165802400#!/compare/1503705600/1503792000

Buyer: https://backpack.tf/profiles/76561198160569884#!/compare/1503792000/1503878400

X = 13

Sale 7:

Sold for 13 keys + < 0.5 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198079578383#!/compare/1499731200/1499817600

Buyer: https://backpack.tf/profiles/76561197996904846#!/compare/1499731200/1499817600

X = 13

Sale 8:

Sold with a couple keys for Dead Presidents Brainiac

Seller: https://backpack.tf/profiles/76561198353783512#!/compare/1503014400/1503100800

Buyer: https://backpack.tf/profiles/76561198128939937#!/compare/1503014400/1503100800

Should be used on the Brain.

Sale 9:

Sold for an unusual SMG

Seller: https://backpack.tf/profiles/76561198258632663#!/compare/1500854400/1500940800

Buyer: https://backpack.tf/profiles/76561198316071886#!/compare/1500768000/1500940800

Can be used to update the SMG

Sellers:

Offers:

http://www.tf2outpost.com/trade/29355316 - 2 weeks

Sales at:

13 (2x)

14 (2x)

15 (2x)

19

19 is a clear outlier, and is guaranteed to be lower if we knew the B/O. Excluding 19.

13 quicksold. Excluding 13.

Going with 14-15.