There are no copyright marks on the poster. It can be dated by the performance days, shown and by this link to a now defunct Fillmore website which shows a smaller image of the poster and gives the dates as February 4, 5, and 6, 1966. This was the first non-benefit concert held by Graham at the Fillmore. Graham moved his concerts from the Fillmore Auditorium in July 1968. After the move, the venue was renamed Fillmore West, as he also opened in New York City by then at the Fillmore East.
A copyright search on Bill Graham turns up sound and motion picture recordings and concert posters with much later dates, but nothing pertaining to this particular concert poster. There is no evidence copyright is or has been claimed on this image.
United States Copyright Office page 2 "Visually Perceptible Copies The notice for visually perceptible copies should contain all three elements described below. They should appear together or in close proximity on the copies.
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.
Quest'opera è nel pubblico dominio perché pubblicata negli Stati Uniti fra il 1929 e il 1977, inclusi, senza un avviso di copyright. A meno che l'autore non sia morto da molti anni, non è nel pubblico dominio nei Paesi o nelle aree che non applicano la regola della durata più breve per le opere statunitensi, come Canada (50 pma), Cina (50 pma, ma non Hong Kong o Macao), Germania (70 pma), Messico (100 pma), Svizzera (70 pma), e altri Paesi con trattati individuali. Vedi questa pagina per ulteriori informazioni.