This is gin (typically London Dry or Plymouth) that is 100 English proof (57% ABV), the strength required in the 1800s by the British Royal Navy. The reason being that at 100 English proof, gun powder could still be ignited if gin spilled on it. Use Navy Strength gins for times when you want a cocktail that may otherwise seem watered down if regular strength gin was used, or when you’d like to sip your gin (especially on a cold winter night).