11 months old price!

Sale 1:

Sold for 40 keys

http://www.tf2outpost.com/trade/28781433

http://backpack.tf/profiles/76561198053743602#!/compare/1487462400/1487721600

http://i.imgur.com/m86bfvW.png

Sale 2: (seems strangely low)

Sold with Unusual Butcher Bird Grenade Launcher for Nether Trail Hellmet + 5 keys

http://www.tf2outpost.com/trade/28748113

http://backpack.tf/profiles/76561198083214810#!/compare/1486857600/1487030400

Sale 3:

Sold for 37 keys

[no outpost trade]

http://backpack.tf/profiles/76561198161347782#!/compare/1487030400/1487116800

http://i.imgur.com/mhxinup.png (credits to -GoV-Merp for the screenshot)

Conclusion:

Two valid pure sales at 40 and 37 keys. Taking a final range of 37-40 keys.

Feel free to support/counter my suggestion!