Leopold Bros 8yr Cask Strength Three Chamber Finished BourbonThe Leopold Bros 8 year old cask strength Bourbon is not just the oldest whiskey the company has released in their history it's also the highest in proof. The distillery fills all of their barrels at 50% ABV and, over the course of just a few years in their earthen floor, dunnage style warehouse, they don't see much fluctuation in proof. However, after 8 years of steady maturation, the distillery is starting to see a bit more evaporation of water,