The photo has no copyright markings on it as can be seen in the links above and in the unedited copy of the file.
It can be dated by the history of the group. They formed in the early 1960s, broke up in 1970, and reunited in 1978.
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.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.
The original description page was here. All following user names refer to en.wikipedia.
Upload date | User | Bytes | Dimensions | Comment
2011-08-04 14:30 (UTC) | We hope | 107825 (bytes) | 589×762 | Photo has been cropped. Previous upload was to establish source, timeframe and that there are no copyright marks on it.
2011-08-04 14:29 (UTC) | We hope | 102508 (bytes) | 1670×1024 | {{commons ok}} {{Information |Description=Promotional photo of Peter, Paul and Mary. |Source=[http://cgi.ebay.com/1970-PETER-PAUL-MARY-Legendary-Group-Press-Photo-/150625573165?pt=Art_Photo_Images&hash=item2311fbd92d#ht_2618wt_1164 eBay item] [http://i101
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Peter, Paul and Mary. Paul Stookey on the left of the group.
(Original text) : {{commons ok}} {{Information |Description=Promotional photo of Peter, Paul and Mary. |Source=[http://cgi.ebay.com/1970-PETER-PAUL-MARY-Legendary-Group-Press-Photo-/150625573165?pt=Art_Photo_Images&hash=item2311fbd92d#ht_2618wt_1164 eBay