Is copyright notice required?
Effective March 1, 1989 display of copyright notice is no longer required under the Berne Convention Implementation Act.
Copyright Education Series Foundations Workbook--Copyright Clearance Center
Under the Copyright Right Act of 1909 works published without copyright notice went into public domain upon publication.
For works published between January 1, 1978, but before March 1, 1989, no corrective steps are required if:
The notice is omitted from no more than a relatively small number of copies or phonorecords distributed to the public; or
The omission violated an express written requirement that the published copies or phonorecords bear the prescribed notice.