The "Spot" whiskeys are named for the tradition of the old merchants, who used to mark different casks with a daub or "spot" of colored paint to mark them. The Yellow Spot 12yr Irish whiskey is an age-statement bottling, meaning that the minimum age of the whiskey will be 12 years... considerably older than the venerable Green Spot. This particular label was retired in the 1950s but reintroduced in the new century. Along with the American oak and Spanish sherry, there is a third marriage of Malaga wine casks, which introduces an additional sweet note to the whiskey.
Mitchell & Son is better known for Green Spot Irish whiskey, which considers itself a "pot still whiskey." We take this to mean that it is made in traditional pot stills in batches rather than the more common continuous column still. The brand has been around since 1925 (according to the write-up at Irish Whiskey Notes). The whiskey is made at Midleton (the same distillery that makes Jameson) but made exclusively for Mitchell & Son of Dublin, who has sole distribution rights. The story is an interesting one where the tradition of retailers bottling their own whiskey survives in the label of Green Spot. It is made in limited amounts each year (around 6,000 bottles) from whiskey aged 7 to 8 years in a marriage of traditional oak and Oloroso sherry cask finish.