Only two in existence.

Level 75 - Sold for Smoking Stahlhelm + little sweets (about 1.66-2) You can check item history to see trade history. And the smoking stathalm is with the seller now.

http://www.tf2outpost.com/trade/11348532

Only one seller who is has set B/O to 2 buds

http://www.tf2outpost.com/trade/11348532

1 Sold for strange gunslinger 1 month ago whose price that time was 1.5 to 1.7 bud.

http://www.tf2outpost.com/trade/10400476

Not going into too much of past time (considering recent time)

With one sale of 1.5(gunslinger) and other sale of 1.7 (smoking stathalm+ sweets) and knowing there are only two of these hats exist. I think 1.5-1.7 is good range.

Also note that the last set price was 8 months ago.

http://backpack.tf/vote/id/5089d46c49d7b8c54e00003a