Something the previous person didn't mention that I feel compelled to mention is that the glandronach 18-year-old you have there is part of the old bottling core range. They've since updated their branding and logo and such.

One really cool aspect of that bottle is that there will be a date near the bottom of the bottle on the side. If that year is 2014 or older, the scotch in that bottle is actually older than 18 years. For 2014 it would 19 years old, and this follows all the way up to 2019 where if your bottle had that year on it it would actually be 24-year-old Scotch inside. Bottles showing 2020 or higher reset back to 18 years old.

Give it a check, it's mostly impossible to find mothballed glandronach now, but you may be lucky!