Exclusively aged in Oloroso sherry casks, this has been favourably compared to the now very, very pricey (an unobtainable) Macallan Gran Reserva. Once one of the best rich and heavily sherried whiskies available, the Glendronach 15 year old was discontinued in 2015 due to a shortage of maturing stock after the distillery's five year mothballing between 1996 and 2001.  Sherry matured whiskies of this quality are extremely difficult to source these days, thanks to a flourishing worldwide market and a scarcity of suitable barrels.