Traditionally made with equal parts gin, Green Chartreuse, maraschino liqueur, and lime juice, but like many others (when using a 40%-43% alc./vol. gin)...
For those not a fan of Maraschino, worth a mention is the “Spring Feeling” from The Savoy Cocktail Book 1930. 1/4 lemon juice, 1/4 Green Chartreuse, 1/2 Plymouth Gin.