Please note this is my 1st unusual suggestion, go easy on me, any feedback is appreciated.

3 In existance, 3 on the market.

One has a B/O of 3 buds, another one has a B/O of 3.5, and the last one has a B/O of 5buds.

First Sale: http://www.tf2outpost.com/trade/12320210

Sold for vivid plasma Honcho's Headgear (2.75buds, 2.47 w/ overpay)

Second Sale: http://www.tf2outpost.com/trade/13011045

Sold for 2buds+bigkill+4keys : (2.65buds)

Third Sale: http://www.tf2outpost.com/trade/12715767

Sold for a Steaming Noble Ammassment of Hats: (1.55buds) outlier?

Forth Sale: http://www.tf2outpost.com/trade/12842789

Sold for a Die Job Unusual Nuts n Bolts Conjurer's Cowl (18 keys ?) + Max Head (2.2buds + 18 keys = 3.02 buds, w/ overpay applied on the Cowl 2.93 buds)

http://imgur.com/7FDXs9F (Thanks to [BG]Cokoboko for providing the screenshot :D )

Feel free to correct me.