Pour all the ingredients over ice in a mixing glass and stir as you would a Martini. Strain into a chilled cocktail glass and garnish with the lemon peel.
Bill Grimes, in his wonderful book Straight Up or On the Rocks, reveals the origin of the name of this scotch Manhattan: a Broadway show called Rob Roy. In the original The Savoy Cocktail Book (1930), Harry Craddock calls for equal parts of scotch, sweet vermouth, and dry vermouth, but that might be a tad sweet for today's drinker. This is also called Affinity.