This is exactly how they'd be able to tell. It's possible to tell if a bottle of wine was actually made before 1945 by the presence of radioactive isotopes on the liquid. If certain isotopes are present, the wine was made after the first nuclear explosion, if they're absent, it's older then 1945.
But the thing is, we haven't had an open air nuclear blast since a Chinese test in 1980, given the half life of isotopes, it's possible to date when a person lived. Future generations will have smaller concentrations of radioactive isotopes in their bodies than we do.
This is exactly how they'd be able to tell. It's possible to tell if a bottle of wine was actually made before 1945 by the presence of radioactive isotopes on the liquid. If certain isotopes are present, the wine was made after the first nuclear explosion, if they're absent, it's older then 1945.
But the thing is, we haven't had an open air nuclear blast since a Chinese test in 1980, given the half life of isotopes, it's possible to date when a person lived. Future generations will have smaller concentrations of radioactive isotopes in their bodies than we do.