Function seal_versions 

pub fn seal_versions(
    paths: &[PathBuf],
    certs: &Certs<'_>,
    find: &mut dyn FnMut(&str) -> Vec<PathBuf>,
    judged: &mut Judged,
    hold: Hold<'_>,
) -> Sealed

Earlier versions of those copies (paths, each a file), judged as the copies are, encrypted again to your own certificates, each under hold as above: only “Put back” reads them, which then opens a sealed one with your key at Send.