I found a 1917 cent with a metal detector under the old elm tree at my old house(built in 1933) and I thought I was hot chit for finding something even that old. Cannot imagine finding something a couple of hundred years old.
There's a lot of really ancient houses up here mines ca 1785 I make a good part of my living working on them
I found a 1917-S dime on top of the dirt just outside the back door of a house my family just moved into the day before. About nine years later my mother was removing a shelf out the wall and a 1912 Barber dime fell out from behind it. The house was built in the 1860's. A former neighbor of mine, an electrician, found five Kellogg & Company $20.00 gold pieces in a sock in a wall of the attic of a house they were rewiring in Marysville, CA. He gave the other two guys he was working with one each and kept the other three for himself. They should have given all five to the owners of the house.
And who knows if they are done yet! And one of the really amazing things about his collection is that there were NO regular issue Federal coins in it.