MLA
Son, D. Murphy's. Union Patriotic Envelope with Jefferson Davis Cartoon - "Jeff The Dictator...Jeff The Dig-Tater-Er", Published by D. Murphy's Son. D. Murphy's Son, Print, 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 21, Folder 4. https://digital.library.emory.edu/purl/136h189467-cor.
APA, 6th edition
Son, D. M. (1861). Union patriotic envelope with Jefferson Davis cartoon - "Jeff The Dictator...Jeff The Dig-Tater-Er", published by D. Murphy's Son (Box 21, Folder 4) [Envelopes]. D. Murphy's Son, Print; Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/136h189467-cor.
Chicago
Son, D. Murphy's. “Union Patriotic Envelope with Jefferson Davis Cartoon - ‘Jeff The Dictator...Jeff The Dig-Tater-Er’, Published by D. Murphy's Son.” Envelopes. Civil War Collection. New York City, NY: D. Murphy's Son, Print, 1861. Box 21, Folder 4. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/136h189467-cor.