“This is my grandfather’s axe. The handle has been replaced five times and the blade three times. But this is my grandfather’s axe.” *A dwarf character in a Terry Pratchett story.
I have my grandfather's pocket watch, a 110yo Elgin. The innards has new parts, and one of the watch arms (I think it's the hour hand) comes from another watch, but it's still his watch, and it works. My great-grandchild, when I get one, will be completely unable to tell time with it.