Selling below 1.66 ref

http://www.tf2outpost.com/trade/21285762 - 1.11 ref

http://www.tf2outpost.com/trade/21275885 - 1.11 ref

http://www.tf2outpost.com/trade/21210822 - 1.33 ref

http://www.tf2outpost.com/trade/21331820 - 1.33 ref

http://www.tf2outpost.com/trade/21340870 - 1.33 ref

http://www.tf2outpost.com/trade/21318199 - 1.55 ref

Sellers for 1.66

http://www.tf2outpost.com/trade/21085516 - 1 week old, only sold 1.

http://www.tf2outpost.com/trade/21239186 - 5 days, unsold

http://www.tf2outpost.com/trade/21350095 - 1 day , unsold

http://www.tf2outpost.com/trade/21276653 - 3 days, unsold

http://www.tf2outpost.com/trade/21283462 - 3 days, unsold

http://www.tf2outpost.com/trade/21373212 - 4 hours, unsold (YOUNG)

http://www.tf2outpost.com/trade/21257006 - 4 days, unsold

Unsold at 1.66+

http://www.tf2outpost.com/trade/21330419 - 1 day at 1.77 ref

http://www.tf2outpost.com/trade/21276033 - 3 days at 2 ref

http://www.tf2outpost.com/trade/21360013 - 16 hours at 2 ref

http://www.tf2outpost.com/trade/21083430 - 1 week at 2 ref

http://www.tf2outpost.com/trade/21241010 - 5 days at 2 ref

http://www.tf2outpost.com/trade/21358552 - 17 hours at 2 ref

Classifieds

http://backpack.tf/classifieds/?item=Concheror&quality=1&tradable=1&craftable=1

- 2 for 1.33 ref

- 1 for 1.44 ref

- 6 for 1.66 ref

Conclusion

So this is a weird drop, but 1.66 is hard to sell and that's the lowest value... 1.33 - 1.66 is a better range as more sellers are actually willing to go in that range!