MLA

Koch, Frederick R. (Frederick Robinson). Unidentified. Box 20, folder 373. 1874, n.d.. https://collections.library.yale.edu/catalog/2007266.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 20, folder 373"])(1874, n.d.)[Unidentified]. https://collections.library.yale.edu/catalog/2007266.