Original Bud Value suggests a price of 31 Keys or Lower.

No one has tried to do this yet?

There are a load of these overpriced 3rd gens. They seem to like selling for each other.

Sale 1(Unfortunately just as support, because its a week outdated):

Offered on and sold for Australium Medi-Gun

http://www.tf2outpost.com/trade/25905669#latest

(Hat was not duped at the time)

=25 Keys

Sale 2:

Sold for Planets Muffs:

http://backpack.tf/item/3666596962

http://backpack.tf/item/1914698950

=25 Keys

Sale 3:

Sold for DP Ushanka:

http://backpack.tf/profiles/76561198061405421?time=1438063232

=30 Keys

Mini:

Selling at 30 for at least 20 days:

http://i.imgur.com/KpX3bP4.png

Sale 4:

Sold for DBD Milkman:

http://backpack.tf/profiles/76561198061405421?time=1438685476

=25 Keys

Mini:

Sold for TW Das G.

http://backpack.tf/profiles/76561198109885142?time=1438923216

=28 Keys

Sale 5:

Sold on August 20 for 65.78 USD, or 39.41, whichever you think is more realistic

http://backpack.tf/item/2206011342

http://steamcommunity.com/market/listings/440/Unusual%20Fed-Fightin%27%20Fedora

Assuming its 65.78...

=26 Keys

Sale 6:

Sold with Str Pro Original + Aces HKC for Spec Aussie RL

Outlier, would make hat's value to less than 20 Keys

Sale 7:

Sold for TW Raincatcher + 10 Keys

Histories don't match, but that would fall in the middle of this range either way, even if I used it.