Mini.

Sale 1: Sold for 20 keys

http://backpack.tf/profiles/76561198138476703/#!/compare/1457683200/1457769600

Sale 2: Sold for 20 keys

http://backpack.tf/profiles/76561198048500465/#!/compare/1458777600/1458950400

Not sure about this sale, if there's a mistake, please let me know.

Sale 3: Sold for Strange Specialized Killstreak Australium Ambassador[18 keys via mini]

http://backpack.tf/profiles/76561198058326832/#!/compare/1455523200/1455868800

Sale 4: Sold for Purple Confetti Vintage Merryweather[21 keys via mini]

http://backpack.tf/profiles/76561198059842276/#!/compare/1454313600/1454745600

Mini on Ambassador:

Sellers at 18 keys https://gyazo.com/97ec6a6db3e2e5482f5b5560cee1ae9a.png

Mini on Merryweather:

Sold for 21 keys

http://backpack.tf/profiles/76561197961989884/#!/compare/1458111600/1458198000

So I have sales at 18, 20, 20 and 21. Making this a range of 18-21 keys.