The Lemon Drop was intended to represent the flavor of the Lemon Drop candies, which are essentially just citric acid and sugar. So while you may often see triple sec listed as an ingredient for the Lemon Drop, and while it may in fact result in a "better" drink, it isn't an appropriate ingredient for this cocktail since the lemon drop candies don't include any orange flavoring.
Garnish: Lemon wheel
Shake with ice.
Strain into a sugar rimmed cocktail glass.