- Major & Knapp Eng. Mfg. & Lith Co (New York) (1)
- Malleable Iron Range Co (Beaver Dam, Wis, 1925) (1)
- Mangum & Josephine Weeks (Alexandria) (1)
- Mankyūdō (Edo, Japan) (2)
- Map branch, CIA (1)
- Maquet Gr. (1)
- Maquet, Gr. (1)
- Marcel Delboy (1)
- Marcel Picard (1)
- Marion von Schrë der Verlag (Hamburg) (44)
- Mark Hyman Associates, Inc. (Philadelphia) (1)
- Marshall County Land Co. (Warren, Minnesota), 1906 (1)
- Maryland Geological Survey (Baltimore, Md.?) (1)
- Maryland Geological Survey (Baltimoré) (1)
- Maryland Historical Society (Baltimore, Md) (1)
- Maryland State Weather Service, in cooperation with the U.S. Weather Bureau (Baltimore) (1)
- Maryland. Conservation Department. (1)
- Maryland. State Department of Forestry. (1)
- Mason Bros (New York) (1)
- Mason Bros (New York), 1864 (1)
