Former Owner
- Marienstiftsgymnasium1
- Mark Lansburgh1
- Maurice Kann1
- Mayfair Rare Books and Manuscripts1
- Melk Abbey1
- Middle Hill Rare Books & Manuscripts AB (Stockholm, Sweden)1
- Miguel de Mayora1
- Milt Freudenheim1
- Minerva Kaiser1
- Minnis, Katherine1
- Moissac Abbey1
- Monasterio de El Paular1
- Monsieur de Bel Air1
- Mortimer Frank1
- Mrs. F. W. Bartlett1
- Muriel Agnes Fry1
- N. Pauli1
- Nathaniel Sherman Bouton1
- Newman F. McGirr1
- Nicholas B. Scheetz1