MLA

Koch, Frederick R. (Frederick Robinson). Music/Mienne!. Box 326, folder 1797. 1893 Aug 25. https://collections.library.yale.edu/catalog/17473503.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 326, folder 1797"])(1893 Aug 25)[Music/Mienne!]. https://collections.library.yale.edu/catalog/17473503.