Sale 1:

https://backpack.tf/profiles/76561198161264178#!/compare/1532044800/1533081600

https://backpack.tf/profiles/76561198091939967#!/compare/1532995200/1533081600

Sold for Smoking Tyrant Helm

Use there.

Sale 2:

https://backpack.tf/profiles/76561198091939967#!/compare/1532995200/1533081600

https://backpack.tf/profiles/76561198259986634#!/compare/1533081600/1533168000

Sold for 14 keys + ~22 ref

Total is 15 keys.

Sale 3:

https://backpack.tf/profiles/76561198259986634#!/compare/1533081600/1533168000

https://backpack.tf/profiles/76561198043055116#!/compare/1533168000/1533254400

Sold for 15 keys + 20 ref

Total is ~16 keys

Sale 4:

https://backpack.tf/profiles/76561198043055116#!/compare/1533427200/1533600000

https://backpack.tf/profiles/76561198073603633#!/compare/1533427200/1534896000

Sold for P Fetti Toque + 5 keys

Toque Mini:

https://backpack.tf/suggestion/5b9884bbcf6c757bee7daf8d

Suggestion for 14 keys

Total is 19 keys

Sale 5:

https://backpack.tf/profiles/76561198011321852#!/compare/1535673600/1535760000

https://backpack.tf/profiles/76561198028645962#!/compare/1532304000/1535760000

Untrace.

Sale 6:

https://marketplace.tf/items/434;5;u58

Sold for 34.3 USD

Keys at 1.88 USD

Total is 18.22 keys

Total sales @:

15, 16, 18, 19 keys

Buyers up to 14 keys

Considering 16 sold quick,

Calling 15 & 16 the outliers,

Taking 18 - 19 keys