2 years old price!

Sale 1:

Sold for 43 keys

http://www.tf2outpost.com/trade/27677094

http://backpack.tf/profiles/76561198022110827/#!/compare/1459814400/1460160000

http://backpack.tf/profiles/76561198062857508/#!/compare/1460073600/1460160000

Sale 2:

Sold for Duped Sunbeams Détective Noir* + 5 keys + sweets (~2) = >50 keys (B/O caps it at 50 keys)

http://www.tf2outpost.com/trade/28090711#latest

http://backpack.tf/profiles/76561198031371895/#!/compare/1461110400/1461196800

http://backpack.tf/profiles/76561198071601053/#!/compare/1461110400/1461196800

Sale 3: (outlier)

Sold with Professional Australium Stickybomb Launcher for Circling Heart Chieftain's Challenge

http://www.tf2outpost.com/trade/28087017

http://backpack.tf/profiles/76561198154701068/#!/compare/1460764800/1461024000

Sale 4:

Unable to identify sale

http://www.tf2outpost.com/trade/27931718

http://backpack.tf/profiles/76561198054758757/#!/compare/1457337600/1457424000

Mini-suggestion for Duped Sunbeams Détective Noir*:

http://www.tf2outpost.com/trade/28036172 - C/O of 50 keys and a declined offer of 45 keys

Conclusion:

Two valid sales at 43 and 50 keys. Taking a final range of 43-50 keys.

Feel free to support/counter my suggestion!