Here is my suggestion for this Hellfire Das Gutenkutteharen

Special thanks to polar and Foamy the Fearsome

There are 3 in the world and here are the 2 histories

http://lv1.backpack.tf/item/2078364318

http://lv1.backpack.tf/item/2042457570 (duped)

First sale -sold for 57 keys DUPED- not taking into consideration

Sold for a strange australium grenade launcher (19 keys), strange spec ks australium sticky launcher (mini at 20), strange birdman (1 key) and 21 keys pure

[(19+20+1)*0.9] + 21 = 57 keys

Proof

sellers' backpack before the trade: http://backpack.tf/profiles/76561198083646174?time=1426662000

seller's backpack after the trade : http://backpack.tf/profiles/76561198083646174?time=1426748400

*Mini on spec ks aussie launcher:

http://imgur.com/SrxeAgc

sells around ~45€ on average (= ~21 keys)

found a lower B/O on outpost: http://www.tf2outpost.com/trade/25410422 20 keys

Taking 20, counting as 20 keys.

Second sale- sold for 46 pure DUPED- not taking into consideration

Sold for 46 keys pure

sellers' backpack before the trade: http://backpack.tf/profiles/76561198098794519?time=1425921309

seller's backpack after the trade : http://backpack.tf/profiles/76561198098794519?time=1426057200

Third sale sold for 45 keys DUPED - not taking into consideration

Solf for a Strange spec. ks. Australium Force-A-Nature(15 keys),1 key , Essential Accessories painted lime(1 key 10 ref), Lime painted Max's Head (28.5 keys + 10 ref= 29 keys)

*The Max's is non-level 1 or 7 and non-duped so it's considered pure

(15+1.5)*0.9+ 29 + 1 = 44.85 ~ 45

Proof

buyer's backpack before the trade: http://backpack.tf/profiles/76561198058134676?time=1427353200

buyer's backpack after the trade : http://backpack.tf/profiles/76561198058134676?time=1427439600

Forth sale sold for 65 keys ONLY VALID SALE The hat was clean at that time

Offered on a harvest moon platinum pickelhaube and accepted :D (58 keys) +7keys

58*0.9 + 7= 65 keys

proof of being offered: http://www.tf2outpost.com/trade/24527741#latest

proof of trade: http://imgur.com/XqEVRAK