Out of all the thing to rise, this sure wouldn't have been my first guess...

Classifieds (As of 7:15 PM EST):

2 at 1.44, 2 at 1.55, 1 at 1.66, 2 at 2 ref http://prntscr.com/62du85 (This still gets higher despite the lower sellers XD)

Limited market, only 5 unpainted ones have been bumped in the last day on Outpost, 2 are selling for offers, one has sold already, one is a hat swap, and the other one is selling just for "bp.tf prices"

Recent sales:

http://bazaar.tf/trade/1200134 1.66 ref (No, that is not a typo, Bazzar isn't dead yet :P)

Buyers:

http://www.tf2outpost.com/trade/24757704 1.66 ref

Notable offers:

http://www.tf2outpost.com/trade/23799103 Has been offered 1.66 ref pure and 2 ref in items in the last week.

http://www.tf2outpost.com/trade/24673876 1.66 offer in the last week

As no one sells it for 1.55 on Outpost, and 1.66 sells the most, 1.66 flat should be good.