1 of 2 in existence!

Sale 1:

Sold for Molten Mallard Fur-lined Fighter (39*0.9) = 35.1 (rounding to 35 keys)

http://www.tf2outpost.com/trade/27008930

http://backpack.tf/profiles/76561198047577641?time=1442127600 (September 13th)

http://backpack.tf/profiles/76561198047577641?time=1442214000 (September 14th)

http://backpack.tf/profiles/76561198047577641?time=1442214000&compare=1442127600

Sale 2:

Sold for Purple Energy Heavy Duty Rag* (~21) + Strange Festive Minigun (8*0.9) + Sweets (~5.5*0.9) = 21 + 7.2 + 4.95 = 33.15 (rounding to 33 keys)

http://backpack.tf/profiles/76561198007850070?time=1441177200 (September 2nd)

http://backpack.tf/profiles/76561198007850070?time=1441263600 (September 3rd)

http://backpack.tf/profiles/76561198007850070?time=1441177200&compare=1441263600

Sale 3:

Sold with 2 keys for Cloudy Moon Heavy Duty Rag (45.5*0.9) = 38.95 (rounding to 39 keys)

http://www.tf2outpost.com/trade/26778990

http://backpack.tf/profiles/76561198146871410?time=1439967600 (August 19th)

http://backpack.tf/profiles/76561198146871410?time=1440054000 (August 20th)

http://backpack.tf/profiles/76561198146871410?time=1440054000&compare=1439967600

Mini-suggestion for Purple Energy Heavy Duty Rag*:

http://www.tf2outpost.com/trade/26898258 - B/O of 25.5 keys (>2 weeks)

http://www.tf2outpost.com/trade/27043430 - B/O of 26 keys

Sold for Miami Nights Hound Dog (23.5*0.9) = 21.15 (rounding to 21 keys)

http://backpack.tf/profiles/76561198026639685?time=1440658800 (August 27th)

http://backpack.tf/profiles/76561198026639685?time=1440745200 (August 28th)

http://backpack.tf/profiles/76561198026639685?time=1440745200&compare=1440658800

~Taking a value of 21 keys

Notes:

http://www.tf2outpost.com/trade/26778990 - B/O of 40 keys

Conclusion:

Three valid sales at 35, 33, and 39 keys. Taking a final range of 33-39 keys.

Feel free to support/counter my suggestion!