The original liqueur formulated by Brother Antoine from the 'elixir' (Chartreuse Elixir Végétal). Green Chartreuse is flavoured with extracts from 132...
Curious how long this keeps. I inherited a bottle from my Grandfather which was probably bought (and opened) in the late 1980's. Still tastes fine to me...
As long as the screwcap was replaced to prevent evaporation, it will still taste great. It would be interesting to compare taste to modern-day Chartreuse.