12 ref = 0.74 keys = 7 keys (rounded down).

Top Classifieds:

http://gyazo.com/839c383ff0eef11eacc0c4fc396fc70a

1x 12 ref

2x 13 ref

2x 14 ref

1x 15 ref

1x 16 ref

3x 1 key

Sellers at 12 ref:

http://www.tf2outpost.com/trade/24916115

http://www.tf2outpost.com/trade/25273896

http://www.tf2outpost.com/trade/25161148

http://www.tf2outpost.com/trade/25195095

Sellers at 13 ref:

http://www.tf2outpost.com/trade/25248333

http://www.tf2outpost.com/trade/25166876

Sellers at 13.66:

http://www.tf2outpost.com/trade/25107961

Sellers at 14 ref:

http://www.tf2outpost.com/trade/25249640

http://www.tf2outpost.com/trade/25274063

Sellers at 15 ref:

http://www.tf2outpost.com/trade/25278677

http://www.tf2outpost.com/trade/25273702

http://www.tf2outpost.com/trade/25276811

Sellers at 15.33 ref:

http://www.tf2outpost.com/trade/25236196

Sellers/Sold at 1 key:

http://www.tf2outpost.com/trade/24853163

http://www.tf2outpost.com/trade/25187986

http://www.tf2outpost.com/trade/25258271

http://www.tf2outpost.com/trade/25186025

http://www.tf2outpost.com/trade/25259414

http://www.tf2outpost.com/trade/25237380

http://www.tf2outpost.com/trade/25279201

http://www.tf2outpost.com/trade/25281517

http://www.tf2outpost.com/trade/25256145

As always, please try and keep the comments relevant, please don't make comment comprised only of "upvote" or "downvote". Counter-proof / supportive proof is always appreciated!