Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:Le_Kef_-_Abside_de_la_basilique_Saint-Pierre.jpg
It is an anonymous work or pseudonymous work and 50 years have passed since the date of its publication (or creation, whatever date is the latest)
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Before July 5, 2009, a photographic work was protected for 25 years. Pictures created before July 5, 1984 have already been placed into the public domain.