User blog comment:Mattd43/Public Domain Space Heroes./@comment-69.132.1.233-20131031022347/@comment-6417519-20131031193935

See the FAQ for works post-1923. 1923 - 1963 had to be renewed in the 28th year. If not, PD. 1964 - 1977 had to have a proper copyright notice. If not, PD. 1977 - present has to do with life of the creator.