Before the year 1989, use of a copyright notice — consisting of the copyright symbol (©, the letter C inside a circle), the abbreviation “Copr.”, or the word “Copyright”, followed by the year of the first publication of the work and the name of the copyright holder — was part of United States statutory requirements. Several years may be noted if the work has gone through substantial revisions. The proper copyright notice for sound recordings of musical or other audio works is a sound recording copyright symbol (℗, the letter P inside a circle), which indicates a sound recording copyright. Similarly, the phrase “All rights reserved” once asserted a copyright.
In 1989, the U.S. enacted the Berne Convention Implementation Act by amending the 1976 Copyright Act. As a result, the use of copyright notices has become optional to claim copyright, because the Berne Convention makes copyright automatic. The lack of notice of copyright using these marks may have consequences in terms of reduced damages in an infringement lawsuit — using notices of this form may reduce the likelihood of a defense of “innocent infringement” being successful.