The three casks they chose for this Macallan 50 Year Old bottling were all filled on the same day, 14th January 1949, and were matured in Speyside over 50 years. Each cask was almost identical in strength (between 50.2% and 50.8% abv) when they tipped them ready for the marrying period which started on 12th May 1999, each having lost the same amount of alcohol through evaporation over those 50 years. This means that each butt (holding 500 bulk litres when filled) has contributed a third of the vatting, and thus a third of the character of the 50 years old. The amount of whisky left in the cask after their 50 year slumber was only 48% of that which was originally filled.