Sale 1:

Quicksold for 17 keys

Seller: https://backpack.tf/profiles/76561198170427507#!/compare/1546473600/1546560000

Buyer: https://backpack.tf/profiles/76561198273772926#!/compare/1546387200/1546560000

https://backpack.tf/item/5038393160

X = 17

Sale 2:

Quicksold for 15 keys + ~1 key in items

Seller: https://backpack.tf/profiles/76561198050226685#!/compare/1546473600/1546560000

Buyer: https://backpack.tf/profiles/76561198170427507#!/compare/1546473600/1546560000

https://backpack.tf/item/5038393160

X = 16

Other Sales:

https://backpack.tf/item/5038393160 (#1-3)

#1

Bulk for Green Energy Shellmet

https://backpack.tf/profiles/76561198367617045#!/compare/1546214400/1546300800

https://backpack.tf/profiles/76561198119577562#!/compare/1545868800/1546214400

#2

Untraceable, only some keys match

https://backpack.tf/profiles/76561198119577562#!/compare/1546473600/1546560000

https://backpack.tf/profiles/76561198050226685#!/compare/1546473600/1546560000

#3

Untraceable

https://backpack.tf/profiles/76561198273772926#!/compare/1546387200/1546560000

https://backpack.tf/profiles/76561198072355915#!/compare/1546473600/1546560000

Sales at:

16

17

No current sellers.

These are the only sales we have to work with, and the item has been dumped into tf2mart and has remained there for over 2 months now. Should be fine to use these sales. Will keep the highest quickselling point, however. Excluding 16.

Supporting this drop, the item appears to have sold to tf2mart for a bubbling modest:

https://backpack.tf/profiles/76561198072355915#!/compare/1546473600/1546560000

https://backpack.tf/item/5038393160

https://backpack.tf/item/1360958852

Not a fan of using tf2mart sales, but it can be used as support here.

The modest has a seller at 17.5 currently:

https://backpack.tf/stats/Unusual/Modest%20Pile%20of%20Hat/Tradable/Craftable/34

Going with 17 flat.