To test the metrics and certification process, project staff conducted test audits of three repositories of digital content maintained by third-party organizations:

• Koninklijke Bibliotheek (KB): The national library of the Netherlands maintains the official digital archive for Elsevier Science Direct journals, electronic journals published by Reed Elsevier Ltd. Elsevier is the world’s largest publisher of scientific, technical, and medical research information. Under its arrangement with the KB, the latter receives digital copies of all Elsevier journals made available on its Web site. The archiving of Elsevier-published digital content by a trusted digital repository is considered an important term in the publisher’s contracts with subscribing libraries and universities. The archive includes the electronic contents of the publisher’s approximately 1,500 Science Direct journal titles covering all areas of science, technology, and medicine, and exceeds 7 terabytes of data.
• Portico: Under the umbrella of Ithaka Harbors, Inc., Portico preserves scholarly literature published in electronic form and ensures that these materials remain accessible to future scholars, researchers, and students. Portico is a centralized preservation repository designed to distribute preservation costs and benefits among academic institutions, libraries, publishers, and government agencies. 
• Inter-university Consortium for Political and Social Research (ICPSR): ICPSR maintains and provides access to a vast archive of social science data for research and instruction. The ICPSR data holdings contain some 6,000 studies and 450,000 files that cover a wide range of social science areas such as population, economics, education, health, social and political behavior, social and political attitudes, history, crime, aging, and substance abuse. A unit within the Institute for Social Research at the University of Michigan, ICPSR is a membership-based organization, with more than 500 member colleges and universities around the world. A council of leading scholars and data professionals guides and oversees the ICPSR activities.
• LOCKSS: The project also audited one distributed archiving system: the LOCKSS system developed by Stanford University. The LOCKSS system was originally developed as a peer-to-peer software that functions as a persistent access preservation system for Web-based publications.