Using last month.

Sale 1:

Sold for 6 keys + 10 ref

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1524009600/1524096000 – near ID: 6789410231

Buyer: https://backpack.tf/profiles/76561198191120537#!/compare/1523836800/1524096000

Untraceable, apart from the 10 ref (Near ID) in the seller’s end and the key histories below. Bot.tf confirms though: https://i.imgur.com/Vrn5mdW.png

https://backpack.tf/item/6789410217

https://backpack.tf/item/6789410247

https://backpack.tf/item/6789410258

https://backpack.tf/item/6789410274

https://backpack.tf/item/6789410281

https://backpack.tf/item/6789410296

X = 6.5

Sale 2:

Sold for 6 keys + 10 ref (Buyer’s compare link)

Seller: https://backpack.tf/profiles/76561198305676157#!/compare/1524528000/1524614400

Buyer: https://backpack.tf/profiles/76561198032176942#!/compare/1524528000/1524614400

Bot.tf confirms: https://i.imgur.com/Vrn5mdW.png

X = 6.5

Sellers:

15 keys:

https://i.imgur.com/vGKEj8F.png

https://backpack.tf/item/6020575796

20 keys:

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

https://backpack.tf/item/5439323216

Offers:

http://www.tf2outpost.com/trade/29632194

May seem low, but the ~$18 on the SCM (~7.5 keys) supports: https://i.imgur.com/7MGj9KH.png

Sales at:

6.5 (2x)

Going with 6.5 flat.