Cask 307 refers to a particular oak cask used in the aging of Macallan single malt Scotch whisky. It became famous for producing a highly sought-after and valuable whisky, contributing to the reputation of Macallan as a premium brand.
The exact reason for the unique character of the whisky from Cask 307 is not fully understood, but it is believed to be a combination of factors, including the specific type of oak used, the age of the wood, and the conditions under which the whisky was stored. The whisky aged in this cask developed a rich, complex flavor profile with notes of dried fruit, spice, and oak, and was highly prized by connoisseurs.