Former Owner
- Ohio State University Center for Epigraphical and Palaeographical Studies1
- Ohio State University School of Music1
- Oliver Henry Perkins2
- Oliver R. Barrett4
- Omaha Public Library1
- Orlandus de Fatiis1
- Oswald Carl Friedrich von Seilern und Aspang2
- Otto Ege120
- Otto Haas1
- Otto Jahn1
- Otto Orren Fisher2
- Otto Vollbehr3
- Owen D. Young1
- P. Desq1
- P. J. De Mat1
- P. Pigeot1
- PBA Galleries1
- Pangracius Chrewczer1
- Paolino Gianfilippi1
- Paolo Gallo1