Repost of my previous suggestion. I think 2 ref is the most common price. With patience, it might be possible to sell for a bit more, but no-one is selling at 1.66 ref at the moment.

http://www.tf2outpost.com/trade/6627699 - Sold for 2 ref

http://www.tf2outpost.com/trade/6142260 - Sold for 2 ref

http://www.tf2outpost.com/trade/5468730 - Sold for 2 ref

http://www.tf2outpost.com/trade/6401016 - Sold for 2 ref

http://www.tf2outpost.com/trade/5323606 - Sold for 2 ref

http://www.tf2outpost.com/trade/6667729 - Selling for 2 ref

http://www.tf2outpost.com/trade/6668715 - Selling for 2 ref

http://www.tf2outpost.com/trade/6699687 - Selling for 1.77 (only 1 I could find < 2 ref, but still more than 1.66)

The last price was set a month ago, and I think the market has moved on.