The Old Pal Cocktail first appears in "Barflies and Cocktails" (1927) by Harry MacElhone of the famed Harry's New York Bar in Paris. There it was listed as using sweet vermouth, but in the 1930 edition of "ABC of Mixing Cocktails" he changed the recipe to use dry vermouth instead. While you will often find bartenders these days using American Rye whiskey for this drink, I find that Canadian whisky provides a little better balance with the dry vermouth.