Copy-pasting the proof:

2 of these exist

1st:

http://www.tf2outpost.com/trade/6985758 offer of a Storm KE (8)

2nd:

http://www.tf2outpost.com/trade/7087670

Stormy KE + Portal Box offer made here http://www.tf2outpost.com/trade/6697766

Has a B/O of 10 that has maybe been met

Previous owner:

http://www.tf2outpost.com/trade/6527720 - can only tell that the lower row in here http://www.tf2outpost.com/trade/6482417 was involved in the trade (4.3+1+1.3+.3, ~7)

Previous previous:

http://www.tf2outpost.com/trade/6497198 quicksold it, infinity's offer was hidden but he was the new owner, can only assume he made a better offer. So quicksold it for 5+

First owner:

http://www.tf2outpost.com/trade/5569055

Apparently took the Lanter + keys offers as he had the Lanter tower afterwards http://www.tf2outpost.com/trade/5570673 (~8 Buds)

So in conclusion this hat hasn't moved much, but has C/Os worth 7+ and has sold for that much in the past. Can't tell so far if the 10 buds B/O will be met, but if so, maybe make a price change in the future