Dumbarton 1974 Single Grain 

An incredibly rare offical bottling from the long-gone Dumbarton distillery. This whisky has been "Vatted and bottled from selected barrels". 

Dumbarton is a closed grain distillery, known for using American-style stainless steel columns rather than the traditional Coffey stills. Only using maize (instead of wheat or barley) meant that the spirit possessed quite a heavy character. Rarely bottled as a single grain, the overwhelming majority was used in the Ballantine’s blend. The distillery itself shut in 2002, and is now demolished.

This was distilled in 1974 and bottled at some point in the 1990s.