Charlotte twists up the classic Army and Navy Cocktail which first appears in print in David Embury's The Fine Art of Mixing Drinks. Embury described it as a Gin Sour that uses orgeat instead of simple syrup. In this version, Charlotte uses Sailor Jerry Spiced Rum, thus the different name.
2 parts Sailor Jerry Spiced Rum
3/4 part orgeat syrup
1 part fresh lime juice
Shake with ice.
Strain into a chilled cocktail coupe.
Garnish with grated nutmeg.