Jack's Manual by J. A. Grohusko (1910, p.35)

0.5 portionScotch whiskey base
0.25 portionFrench vermouth modifier
0.25 portionItalian vermouth modifier
2 glassesice — cracked iceother
  1. Stir the Scotch whiskey and both vermouths with cracked ice until very cold.
  2. Strain into a bar glass and serve.

Ice: Cracked ice

See also: Bagardie Cocktail, Tuxedo Cocktail

Source says to frappe and serve in a bar glass.