Interpol’s Most Wanted – Art
Interpol releases a poster (interpol.int, 2012) every June and December to publicize the Most Wanted Works of Art. The list shows a mixture of the most famous artists and lesser known, but still very valuable works.
Their ‘recovered art’ collection is quite impressive, and there are still a few ‘unclaimed items’ that are not currently for sale.
International Microcosms by Keuder 
http://archives.icom.museum/object-id/publications.html
“Object ID is an international standard for describing cultural objects. It is the result of years of research in collaboration with the museum community, international police and customs agencies, the art trade, insurance industry, and valuers of art and antiques.”