Sale 1:

Sold for 14 keys + 20 ref (> 0.5)

No outpost

Seller: https://backpack.tf/profiles/76561198176125115#!/compare/1501632000/1501891200

Buyer: https://backpack.tf/profiles/76561198078631985#!/compare/1501804800/1502064000

X = 15

Sale 2:

Sold for 15 keys

No outpost

Seller: https://backpack.tf/profiles/76561198094730000#!/compare/1502409600/1502496000

Buyer: https://backpack.tf/profiles/76561198183960699#!/compare/1502409600/1502496000

X = 15

Sale 3:

Sold for Pro. KS Blood Botkiller Rocket Launcher (~13) + skin (2)

http://www.tf2outpost.com/trade/29231206 - B/O of 14

Seller: https://backpack.tf/profiles/76561198045174236#!/compare/1498262400/1498348800

Buyer: https://backpack.tf/profiles/76561198175151593#!/compare/1498262400/1498348800

X = 14 (Capped by B/O)

Sale 4:

Sold for Dead Presidents Scotsman’s Stove Pipe (14)

http://www.tf2outpost.com/trade/29350425 - B/O of 12.5

Seller: https://backpack.tf/profiles/76561198257431796#!/compare/1504051200/1504224000

Buyer: https://backpack.tf/profiles/76561198375970684#!/compare/1504137600/1504224000

X = 13 (Capped by B/O, rounded)

Sale 5:

Quicksold for 11 keys

No outpost

Seller: https://backpack.tf/profiles/76561198078631985#!/compare/1501804800/1502064000

Buyer: https://backpack.tf/profiles/76561198053747026#!/compare/1501977600/1502064000

X = 11

Sale 6:

Sold for 10 keys

http://www.tf2outpost.com/trade/29332215 - B/O of 16

Seller: https://backpack.tf/profiles/76561198183960699#!/compare/1503446400/1503532800

Buyer: https://backpack.tf/profiles/76561198096673788#!/compare/1503446400/1503532800’

X = 10

Sale 7:

Sold for Miami Nights Tam O’ Shanter

No outpost

Seller: https://backpack.tf/profiles/76561198124999895#!/compare/1503619200/1503705600

Buyer: https://backpack.tf/profiles/76561198112281935#!/compare/1503532800/1503619200

Can be used on the Shanter.

Sale 8:

Sold with 1 key + cheap item for Orbiting Fire Blast Defense

Seller: https://backpack.tf/profiles/76561198259646668#!/compare/1503964800/1504051200

Buyer: https://backpack.tf/profiles/76561198257431796#!/compare/1503964800/1504051200

Should be used on the Blast.

Sale 9:

Bulk for Strange Terror-Watt Rotation Sensation

Seller: https://backpack.tf/profiles/76561198111914012#!/compare/1501545600/1501632000

Buyer: https://backpack.tf/profiles/76561198176125115#!/compare/1501459200/1501545600

Sellers:

13 keys:

https://i.imgur.com/DsboX2a.png

18 keys:

https://i.imgur.com/Xomj31C.png - 10 days

21 keys:

https://i.imgur.com/JWSezHl.png - 8 months

Sales at:

10

11

13

14

15 (2x)

11 quicksold. Excluding 10 and 11.

Going with 13-15.