Kind houseguests left us the gift of a bottle of a Porto Barros, "over 40 years old," says the bottle, and we're not quite sure what it is. I love port, but am still in the learning process. Can't for the life of me find any usable information on this online. I know Porto Barros is known for excellent aged tawnies, but nowhere on the bottle is there a mention of tawny. Does this still mean it's a tawny, given the 40-year specification (versus a specific date)? Should we drink this now, or will it benefit from further aging? Anyone?