You are right in that this has nothing to do with trademarks. Copyright assignments can be researched on this US Government site (here a sample output for "Cloanto"):

https://cocatalog.loc.gov/cgi-bin/doctitles.cgi?V3626D795 https://cocatalog.loc.gov/cgi-bin/doctitles.cgi?V9946D337 https://cocatalog.loc.gov/cgi-bin/doctitles.cgi?V9943D475