Thank you for submitting your item for appraisal. This appears to be one the limited edition bottles of 500, Glenfiddich 50 Years Old, bottled on 26.07.1991BOT., Bottle# 42. A comparable bottle sold for the lower estimate three years ago. Once the whisky is bottled it does not change at all, it does not get better, only very little evaporates. The price paid previously was a in parts tax deductable donation, not a fair market price. Nonetheless a rare liquid, very suitable for the asian market.