MLA

Koch, Frederick R. (Frederick Robinson). Music/Quintet, piano, strings, G. 413-418. Box 63, folder 1405. [1799]. https://collections.library.yale.edu/catalog/2068034.

APA, 6th edition

Koch, Frederick R. (Frederick Robinson). (["Box 63, folder 1405"])([1799])[Music/Quintet, piano, strings, G. 413-418]. https://collections.library.yale.edu/catalog/2068034.