Daly's Bartenders' Encyclopedia by Tim Daly (1903, p.97)

1 wine glassbrandy — brandy (Martel)base
1 pony glassJamaica rum base
1 teaspoonfulsugar base
milk — Fill the glass with milk.dilution
1egg — fresh eggother
0.33 glassice other
nutmeg — Grate a little on top.other
  1. Add the sugar, egg, ice, brandy, and Jamaica rum to a mixing glass.
  2. Fill with milk, shake well, strain into a large bar glass, grate a little nutmeg on top, and serve with straws.

Garnish: Freshly grated nutmeg

Ice: Ice

Daly frames this as a notably swell and nutritious egg drink.

The split-base structure is the key distinction.

See also: Egg Milk Punch, Sherry Wine Egg Nog