1. The symbol © (letter C in a circle); the word “Copyright”; or the abbreviation “Copr.”
2. "The year of first publication. If the work is a derivative work or a compilation incorporating previously published material, the year date of first publication of the derivative work or compilation is sufficient. Examples of derivative works are translations or dramatizations; an example of a compilation is an anthology. The year may be omitted when a pictorial, graphic, or sculptural work, with accompanying textual matter, if any, is reproduced in or on greeting cards, postcards, stationery, jewelry, dolls, toys, or useful articles."

   This was not required for copyrighted photos published before 1978 under Copyright Act 1909, and omission of date may have been irrelevant to such works. However, Copyright Act of 1976 came into effect and then has applied to copyrighted materials published before 1978. Year has become required for works published before 1978. Consequently, pre-1973 copyrighted photos without a year of copyright and registration and required mandatory deposit into the Copyright Office lost copyright protection and then fell already into the public domain.

3. The name of the copyright owner, an abbreviation by which the name can be recognized, or a generally known alternative designation of owner.

   Example © 2007 Jane Doe.

Publicity photos (star headshots) have traditionally not been copyrighted. Since they are disseminated to the public, they are generally considered public domain, and therefore clearance by the studio that produced them is not necessary.

The Professional Photographer's Legal Handbook By Nancy E. Wolff, Allworth Communications, 2007, p. 55:

There is a vast body of photographs, including but not limited to publicity stills, that have no notice as to who may have created them.

Creative Clearance-Publicity photos"

Publicity Photos (star headshots) older publicity stills have usually not been copyrighted and since they have been disseminated to the public, they are generally considered public domain and therefore there is no necessity to clear them with the studio that produced them (if you can even determine who did).