MLA

Koch, Frederick R. (Frederick Robinson). Hainl, Georges. Box 20, folder 370. 1860 Sep 14. https://collections.library.yale.edu/catalog/2007271.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 20, folder 370"])(1860 Sep 14)[Hainl, Georges]. https://collections.library.yale.edu/catalog/2007271.