8 months old.

Sources

http://www.tf2outpost.com/trade/8160476 <-- last sale

http://www.tf2outpost.com/trade/9711102

http://www.tf2outpost.com/trade/9711294

http://www.tf2outpost.com/trade/9048626

Offers, Etc.

Sunbeams Samur-Eye = 19-22.8 buds

Cloudy Moon Ballcap+ Stormy Anger = 15.7-19.5 buds

Harvest Moon Brainiac + Harvest Moon Buckaroo = 17.4-21.2 buds

Burning Tyrant's Helm = 19.1-21.1 buds

SALE for Burning Bicorne + P. Confetti Killer's Kabuto + O. Planets Raincatcher + 3 buds = 20.2-24.4buds

This hat easily gets offers in the 20 bud range (with a current owner claiming a 20 pure offer). I put the lower bound at 19 because there are plenty of offers in that range, and the high value at 21 because the sale was at ~22.