Sharing a great interest for philately has enriched Marjorie and Alvin Robert Kantor's marriage immeasurably. Additionally, their support of the Smithsonian National Postal Museum not only enhanced the museum's foundation in 1993 but also deepened the U.S. collection, helping make it the world's finest. They served on the Council of Philatelists from 1997 through 2004.
Following Bob's graduation from the University of Wisconsin and then service in World War II and Margie's graduation at Northwestern University, Bob became the founding president of the National Bulk Vendors Association. Together Bob and Margie collected U.S. stamps and participated in hobby activities with Bob serving as president of the Chicago Philatelic Society. They began building a philatelic library, which ultimately led to a deep interest in colonial and post-colonial postal history. They collected early postal documents, presidential free franks, and Sanitary Fair stamps and ephemera. They wrote the definitive study on Sanitary Fair issues and in 1993 published A Philatelic and Historical Study of Civil War Benevolences.
Margie and Bob donated twelve significant historical postal documents to the NPM permanent collection in 1984 and 1985. These included, among others, Benjamin Franklin's personal record of the account of the post office in 1770, Bunker Hill hero Joseph Warren's 1775 letter carried by the Constitutional Post of William Goddard, Thomas Jefferson's signature on a document as Secretary of State to establish a post office in 1790, and Goddard's 1774 petition to establish a colonial mail system.