This drink was named for a member of the family which founded the Guion Line, a steamship company which operated from 1866 to 1892 and was one of the primary steamship lines providing transportation from London to New York. This drink was probably created at the Waldorf Astoria bar.
1 1/2 oz gin
1 1/2 oz sweet vermouth
dash of Bitter Truth Orange Bitters
1 bar spoon of Benedictine (on top)
Stir first three ingredients with ice.
Strain into a cocktail glass.
Float the Benedictine on top.