Chill a coupe glass.
Combine the aged rum, sloe gin, apricot liqueur, lime juice and grenadine in a shaker.
Add ice and shake hard for 12 seconds.
Fine-strain into the chilled coupe.
Serve without garnish.
The Savoy Cocktail Book lists four different Millionaires; this is the rum-based No. 1, and the best of them. The others are variously bourbon or gin. Jamaican rum matters — its funk is what keeps the fruit liqueurs honest.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Millionaire.