Fallout is evident in nearly everything made with atmospheric air. It's possible to tell the difference between steel made before 1945 (low-background) and after due to radionuclide contamination. Items made prior to the end of WWII are unlikely to have such trace impurities.
> Since the cessation of atmospheric nuclear testing, background radiation has decreased to very near natural levels,[4] making special low-background steel no longer necessary for most radiation-sensitive applications, as brand-new steel now has a low enough radioactive signature that it can generally be used in such applications
Apparently there’s less money in those scuttled ships now than there was 50 years ago.
