Thats a curious item. I'd bet the alcohol content is probably pretty low now. Sounds like the seal has allowed evaporation of the alcohol. I'd be curious about the origins. You might look at some of the aution sites and get an idea of it's worth.
I've had it stored away for a couple of years now, so my memory of the distiller etc. is vague, but I do remember my father telling me about the sailing ship story when we took it out of my Uncle's house around 20 years ago. If the tale is true, it's something that'll never be made again.