Time travel.
There used to be a neat TV show, few years back, called “Journey Man” about a reluctant time-traveler who’s family, cop brother, and friends didn’t believe what was happening.
He ended up convincing his wife by taking her wedding and engagement rings and burying them underneath the location of their backyard pool during one of his trips decades into the past. When he got home he had her come out, watch as he took a pickaxe to the bottom of the pool, then pull out a lunch box with the rings and a current-day newspaper inside.
It was a great show, that went away far before its time.