"The ultimate expression of handcrafted excellence! Composed of specially selected casks of single malt Scotch whisky (80%) and carefully matured Scottish grain whisky (20%) for binding purposes, the youngest whiskies contained within are a minimum 40 years old. Varying amounts of whisky from former American Bourbon barrels, European hogsheads and former Sherry butts (70 originating from the Speyside region, 25% from the Highlands and 5% from the Lowlands) were married together at 25 years old. After an additional 15 years of aging, this whisky was finished in sherry casks, originating from Jerez, for an additional six months before bottling."
(Official blurb rather than anything I know!)