The original liqueur formulated by Brother Antoine from the 'elixir' (Chartreuse Elixir Végétal). Green Chartreuse is flavoured with extracts from 132...
For those suffering from a Green Chartreuse shortage, I just tried a back to back comparison of Green Chartreuse and Génépy le Chamois in a Last Word. It perhaps loses a little complexity (and ABV) but it still works.