What's the oldest thing you have at home? Is it your home itself? A family heirloom? An old piece of jewelry? Something from a flea market?
I have a pocket watch inscribed with initials that leave both myself and my wife scratching our heads because we're not aware of anyone in the family with those initials. It's one of these "to ABC, from DEF" kind of inscriptions, which should make it easier but doesn't. Our best guess is that it relates to her father's cousin's grandparents but we're not sure. It's dated 1903.
I've got a few coins floating about that date to the 1880s, and a coin that was once a silver half-dollar that's so badly worn you wouldn't know what it was without a bit of research. The date is just about readable - 1870. That's the oldest thing I can think of, off the top of my head. There are a few old things kicking around in dark corners here, so I may yet unearth something older still.