Old Grand-Dad’s lovely and buttery feel on the palate soars with tangy fruit and baked pie flavors. An iconic brand, it remains true to it’s label of “straight” bourbon. To sum it up, Old Grand-Dad is not one for the faint of heart. 100 Proof. For a bourbon to be “Bottled in bond” it means that the whiskey must be the product of one distillation season, one distiller, and one distillery, while being sold at 100 proof and having aged at least four years.