The document discusses how digital collections identify open access content through open content identifiers. It analyzes case studies of four museum collections - the British Library, J. Paul Getty Museum, Walters Art Museum, and Metropolitan Museum of Art - to see where and how they convey licensing terms and what information the identifiers lead to. The identifiers were typically shown below or above image descriptions and always linked to supplemental reuse information. Open content identifiers connect policy, infrastructure, and users regarding openly licensed digital collection content.