I know it hasn't been 3 months, but this hat is priced pretty badly, and the last guy's proof doesn't support anything over a bud well at all, so here we go. This is a combination of last suggestion's proof and new sales from the last month.

http://www.tf2outpost.com/trade/13743339 Sold for 20 keys + Strange All-Father, ~24.

http://www.tf2outpost.com/trade/13811418 Seems to have sold for a bud.

http://www.tf2outpost.com/trade/13743339 B/O of 1 bud, 5 days old

http://www.tf2outpost.com/trade/12448971 B/O of 26 keys, two 1 bud offers, offer of a PEACE Slouch, ~25 keys (Last suggestion said it was a TF Logo one and priced it higher), also an offer of Planets Mongol + Steaming Sack (24 keys)

http://www.tf2outpost.com/trade/13210168 Sold for Flies Chieftan's (19 keys)

http://www.tf2outpost.com/trade/13613987 'Quickselling' for 19 keys, unsure of final sale value. Said he/she would be willing to go as low as 18 keys

http://www.tf2outpost.com/trade/13503103 B/O of 1 bud. Unsure as top what it sold for

http://www.tf2outpost.com/trade/11547759 Sold for Bubbling Kabuto (1 bud)

http://www.tf2outpost.com/trade/12447131 Sold for 19 keys

http://www.tf2outpost.com/trade/13602164 Sold for 21 keys

http://www.tf2outpost.com/trade/13811418 B/O of 23 keys, unsure of what it sold for.

http://www.tf2outpost.com/trade/12209192 Looks like it sold for a Steaming Grimm Hatte (19 keys)

http://www.tf2outpost.com/trade/13549858 Probably sold for 18 keys

http://www.tf2outpost.com/trade/11686519 Sold for steaming Barnstormer (~1 bud, previous suggestion says 1.3 but that price is 7 months old, a suggestion was made a week later lowering the price to 1-1.3, so for the sake of relevance I'm using that.)

http://www.tf2outpost.com/trade/11683951 Sold for a bud

Overall, 18 keys happens but seems to be a quicksell. 19 key sales are more common, 1 bud is possible, and occasionally sales at 1.1 and 1.2 buds (23-25 keys) happen.