Heirloom gravy: If not commonplace, there are still a good number of people who have century-old lu in their freezers.
It's a brown, gravylike liquid that serves as a braising sauce in traditional Chinese cuisine. It is passed from generation to generation -- but it does require upkeep. The lu must be periodically defrosted and cooked for hours in order to maintain its viability.
In old China, food heirlooms weren't that uncommon -- not only lu but also preserved fruit and preserved tea were pretty normal things to hand down to one's children. Those foodstuffs that are still around can be worth tens of thousands of dollars today.
Up next, an heirloom that ran a factory.