Can I Use Louise Brooks Photo?

Dear Rich: I'd like to ask your advice on whether I'm able to use a photo I've seen on the internet of the 1920's actress Louise Brooks for my art work which I would then sell online and through shops on the high street? The photo in question is the one in this link (2nd photo in along the bottom). There is no named photographer attached to it so I assume that no one knows the photographer??? I've seen the same picture on other sites in a better quality so other's have made improvements via photoshop or other software I'm guessing. Any help would be appreciated. We used Google's "Search by Image" feature and found over 600 reproductions of the Louise Brooks image, which either means that the the owner of copyright isn't policing the use -- in which case you're probably fine -- or that the work is in the public domain. Although works published before 1923 are in the public domain, the photograph in question most likely was published after that date as Brooks' film career did not really get going until 1925 when she was signed to a movie contract and began her "degrading enslavement." The photograph also may have fallen into the pubic domain if the copyright was not renewed -- for example, only seven percent of all book copyrights were renewed. Regardless of the PD status, so many reproductions have been published -- and so many of them are by poster merchants -- we assume that you won't be pursued for your reproduction.