No.

Many works are out of copyright and still of known authorship.

Many works are traditional and of known authorship (or at least known publication) - therefore not "anon".

"In public ownership" is an interesting one - what indeed does it mean? Is it the Ghandi statement "I have never copyrighted anything" - despite which the Navajivan Trust polices his copyrights like a hawk! Is it the copyright owner who wills his state to "My country - England"? Is it "Crown copyright"? Is it the quasi-copyright in the King James edition? One thing is sure, if it is supposed to refer to works that are out of copyright, no-one owns them. It is one reason why I have always objected to the expression "public domain" for that tends to imply that the work could again be reduced to private ownership.

Oh, and, to be pedantic, the date of expiry of copyright is the 31st December after the 70th anniversary of the death of the author - no broken years.