Sale 1:

Sold for 18 keys

Seller: https://backpack.tf/profiles/76561198344933095#!/compare/1514937600/1515024000

Buyer: https://backpack.tf/profiles/76561198238743862#!/compare/1514937600/1515024000

X = 18

Sale 2:

Sold for 16 keys

Seller: https://backpack.tf/profiles/76561198163155444#!/compare/1516320000/1516492800

Buyer: https://backpack.tf/profiles/76561198116258680#!/compare/1516320000/1516406400

X = 16

Sale 3:

Sold for Nuts n’ Bolts Samur-Eye + Spec. KS Aussie Axtinguisher (5)

http://www.tf2outpost.com/trade/29475358 - B/O of 14.5

Seller: https://backpack.tf/profiles/76561198125706211#!/compare/1513036800/1513123200

Buyer: https://backpack.tf/profiles/76561198234389156#!/compare/1512864000/1513209600

Will cap at the B/O, however, buyers at ~14.5 on the UT. Excluding this sale.

Sale 4:

Sold for Kill-a-Watt Samur-Eye

http://www.tf2outpost.com/trade/29538753 - No B/O

Seller: https://backpack.tf/profiles/76561198096098198#!/compare/1517270400/1517356800

Buyer: https://backpack.tf/profiles/76561198119899861#!/compare/1517184000/1517356800

Probably better to use on the Samur-Eye. If the Samur-Eye ended up being 19 keys or more, it would be excluded as an outlier due to the 3-month old seller at 19 keys.

Sale 5:

Sold for Fountain of Delight Square Dance

Seller: https://backpack.tf/profiles/76561198119149660#!/compare/1515542400/1515628800

Buyer: https://backpack.tf/profiles/76561198191188271#!/compare/1515542400/1515628800

no

Sellers:

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

17 keys:

https://backpack.tf/item/6534247058

18 keys:

https://backpack.tf/item/5650597591

~18.15 keys:

https://backpack.tf/item/4517937296

19 keys:

https://backpack.tf/item/4339034876 - 3 months

Sales at:

16

18

Going with 16-18.